Energy Efficiency in Traditional Buildings (size 4.7 MB)

Energy Efficiency in Traditional Buildings (size 4.7 MB)
The Advice Series is a series of illustrated booklets published by the
Architectural Heritage Advisory Unit of the Department of the
Environment, Heritage and Local Government. The booklets are
designed to guide those responsible for historic buildings on how
best to repair and maintain their properties.
advice series
advice series
advice series
advice series
advice series
advice series
Understanding how a traditionally built building works and how
to maximise the levels of comfort for its occupants
Choosing the most effective and cost-effective options for
improving energy efficiency
Keeping a historic building in good health
© Government of Ireland 2010
Price a10
Traditionally b uilt buildings pe rform differently fr om modern
construction in the w ay they de al with da mp and atmo spheric
moistu re, and misguided wo rks ai med at improvin g their thermal
efficie ncy can have da maging consequen ces. This guide will help
you to m ake the rig ht decisions on how to increase the comfort and
reduce the energy u se of your histo ric buildin g by giving advice on:
Avoiding damage to the building by inappropriate works
advice series
To be purchased directly from:
Government Publications Sales Office
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Molesworth Street
Dublin 2
or by mail order from:
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Unit 20 Lakeside Retail Park
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Tel: 01 - 6476834/37 or 1890 213434; Fax: 01 - 6476843 or 094 - 9378964
or through any bookseller
© Government of Ireland 2010
ISBN 978-1-4064-2444-7
All or part of this publication may be reproduced without further permission provided the source is
acknowledged. The Department of the Environment, Heritage and Local Government and the authors accept
no liability for any loss or damage resulting from reliance on the advice contained in this booklet
Text and drawings by: Paul Arnold Architects
Contributors: Energy Research Group UCD
All images are by the authors or DoEHLG, except where otherwise stated
Series Editor: Jacqui Donnelly
Design: Bennis Design
What is a ‘traditional’ building?
Embodied energy and whole-life costing
The effects of climate
Planning for warmth
Building use
Heat loss from buildings
Heat transfer through building materials
Thermal bridging
Ventilation and indoor air quality
Thermal mass
Assessment methods
Building Energy Rating (BER) and traditional buildings
Building management
Building condition
Preliminaries to upgrading
Products and materials
Reducing draughts
Windows, doors and rooflights
A Regency house in the city
A detached country house
A pair of rural cottages
A converted stable yard
A mixed-use building in a town
Living over the shop
A converted Georgian townhouse
Places of worship
It is Government policy to reduce energy use and
carbon dioxide emissions from the burning of fossil
fuels. The European Directive on the Energy
Performance of Buildings (2002/91/EC) adopted into
Irish law in 2006, specifically targeted energy
requirements of buildings whether new or existing,
residential or non-residential. In order to meet the
requirements of the directive (which was recast in
2010), and to address the fact that buildings
contribute significantly to this country’s energy
consumption, the standard of energy conservation
required of new buildings has risen significantly in
recent years. Energy performance standards will
continue to rise so that, by 2016, it is intended that
new houses will be mainly passive, that is to say,
designed to consume little or no energy in use.
However, upgrading the thermal efficiency of the
existing building stock presents a challenge,
particularly where the building was built using
traditional materials and construction methods and is
of architectural or historical interest.
People enjoy old buildings for the sense of history
they evoke, the craftsmanship they represent and for
the solidity of their construction. However, there is
sometimes a perception that old buildings are cold. It
is true that they can sometimes be draughty, and the
degree of tolerance shown by their users is testimony
to the value people place on architectural character
and a sense of place, which compensate to quite a
large extent for any shortcomings in comfort.
Historically, heating solutions included a roaring fire or
an ever-burning stove emitting pleasurable warmth.
Of course, our forebears were somewhat hardier than
ourselves, having different expectations in terms of
heat and comfort. Extra clothing and bedclothes, hotwater bottles and even different dietary habits played
their part in keeping people warm in their day-to-day
lives during the colder months. From the midtwentieth century onwards, the availability of cheap
fossil fuels enabled an increasing number of
households to avail of central heating, supplying heat
to all rooms; a concept almost unheard of in earlier
Today, however, there is an increasing awareness of
the importance of energy and fuel conservation. In
tandem with higher expectations in relation to the
general warmth of the indoor environment, this
awareness has led to new standards and types of
building construction intended to ensure that the
energy consumed by a building during its useful life is
minimised. These new standards in modern buildings
have influenced the expectations of users of older
buildings. When dealing with a historic building, there
are other matters which the users and building
professionals who care for old buildings should
address, matters that are to do with the architectural
character of a building, repair and maintenance issues,
older forms of construction and the particular
characteristics of traditional building materials.
A typical brick-fronted, nineteenth-century house
with solid masonry walls, single-glazed sash
windows and slate roof
This booklet sets out to provide introductory guidance
for owners and to act as an aide-memoire for building
professionals and contractors. While the main
objective is to address how the thermal efficiency of
traditionally built buildings can be enhanced, it is
intended to balance this with the conservation of the
architectural heritage. To that end, this booklet
explores ways of improving energy efficiency while
maintaining architectural character and significance,
the intention is to show how to improve the quality of
the architectural environment while maintaining the
historic fabric of traditional buildings.
1. Conservation and Sustainability
Arising from the way they are designed and
constructed, traditional buildings respond to changes
in temperature in very particular ways. Properly
understood, the way traditional buildings behave can
be exploited to make them more comfortable and
more energy-efficient, while saving money on heating
bills. Good architectural conservation is
environmentally sustainable; as a nation we should be
conserving historic buildings not only for their cultural
value but also because it makes environmental sense.
It is important to have realistic expectations of older
buildings, and to find the right use for them. Indeed,
when we appreciate that the designers of these
historic buildings were often concerned with saving
energy, fuel costs historically being even higher than
they are now, we understand that older buildings have
important lessons to teach, with regard both to the
design of new buildings and the repair of existing
ones. In the absence of an understanding of how
traditional buildings and materials behave, modern
technologies may be misapplied and can have
detrimental impacts on historic building fabric.
What is a ‘traditional’ building?
Traditional buildings include those built with solid
masonry walls of brick and/or stone, often with a
render finish, with single-glazed timber or metal
windows and a timber-framed roof; usually clad with
slate but often with tiles, copper or lead. These were
the dominant forms of building construction from
medieval times until the second quarter of the
twentieth century. Less commonly, traditional
buildings had corrugated iron roofs or cladding while
many vernacular buildings were constructed with
stone and/or mud walls and thatched roofs.
The twentieth century saw the development and
widespread use of twin-leafed masonry construction,
commonly called a cavity wall, which is based on a
fundamentally different approach to keeping the
interior of a building dry. The cavity wall consists of an
outer leaf which is presumed always to be wet, and an
inner leaf which it is intended should always be dry,
the two leaves of the wall being separated by an airfilled cavity. In the earliest cavity wall constructions,
the cavity was left empty but latterly was often
partially or totally filled with an insulating material.
A typical traditional farmhouse, built of stone and
finished in lime render, with a slate roof and timber
Traditional masonry walls of stone or brick do not
contain a cavity. In stone construction, the core or
central portion of the wall was often filled with small
stones and lime mortar. While brickwork was often left
exposed externally and plastered internally, rubble
walls were generally rendered externally in a
breathable lime plaster. Solid masonry walls relied on
their thickness to cope with atmospheric moisture,
being sufficiently thick to ensure that drying out took
place before moisture from rainwater passed through
the wall to cause damp on the inner face. The
breathable lime plaster allowed the moisture in the
walls to dry out to the external air. Virtually all
buildings constructed in this country before 1940
were built of this type of masonry construction. The
use of lime extended to other components of the
building; older buildings are often found to have lime
pugging between the joists in the floor, providing
additional thermal and acoustic insulation.
Many traditionally built buildings are protected
structures under the Planning and Development Acts,
and therefore are identified as being of special
interest. However, there are many other traditionally
built buildings that do not have statutory protection
but may nonetheless be worthy of care in their repair
and enhancement for contemporary living.
Dwelling Type
2006 Number
2006 % of Total
Detached house
Semi-detached house
Terraced house
Not stated
Irish dwelling types: This chart indicates that detached buildings represent almost half of all dwellings, which
has implications for energy consumption
% of Dwellings Constructed by Period
Before 1919
1919 to 1940
1941 to 1960
% with central heating
90 100
Solid Fuel
Oil Fired
1961 to 1970
Gas Fired
Dual System
1971 to 1980
1981 to 1990
1991 to 1995
1996 to 2000
2001 or later
Not stated
Age of the Irish housing stock: According to 2006 figures,
approximately 18% of the housing stock dates from
before 1940
Types and percentage of central heating in Irish homes:
There has been a trend towards central heating and
with it higher expectations of thermal comfort
(Source: Energy in the Residential Sector, Sustainable Energy Ireland, 2008. Information adapted from Central
Statistics Office 2006)
Embodied energy and
whole-life costing
It has been said that the greenest building is the one
that is already built. It is important to recognise that
the reuse or continued use of older buildings is a key
component of sustainable development and energyconservation practice. Common sense would suggest
making use of existing buildings before building anew
as demolition waste accounts for a large percentage of
landfill, which is an environmental burden, while the
production and/or importation of new building
materials accounts for a significant amount of energy
use. In addition, the linked concepts of embodied
energy and whole-life costing should be taken into
account in reaching a decision as to what is most
energy efficient.
‘Embodied energy’ is the term used to describe the
energy that was required to extract, process,
manufacture, transport and install building materials
and is now deemed to be embodied in the finished
building. Materials which have been subjected to little
processing or were processed using relatively small
amounts of energy, for example lime mortars (as
opposed to cement mortars), local timber and native
thatch, are therefore low in embodied energy.
Materials such as steel, concrete and modern bricks,
which require a great deal of energy to manufacture,
are higher in embodied energy. Similarly, building
materials transported long distances have higher
embodied energy, as their transport generally requires
the use of non-renewable fuels. Entirely replacing an
existing building with a new one involves a significant
outlay of embodied energy both in the act of
demolition (which includes the waste of existing
materials, some of which are capable of repeated
reuse) and in the use of new materials which have
consumed energy in their production and
‘Whole-life costing’ involves considering not just the
initial capital cost that goes into constructing a
building (including all ancillary design and other
costs), but also the cost of renovation, maintenance
and day-to-day operation over the period of its useful
life. Certain materials have a relatively short lifespan,
yet considerable energy has been used in their
manufacture, while components made of artificial
material are often difficult to repair. For example, the
techniques of repair are well understood for timber
windows and the necessary skills are readily available
whereas uPVC is not easily repaired, potentially
leading to a shorter life for the window unit. Natural
slate requires energy in its extraction and there are
impacts on the environment caused by quarrying.
However, these are offset by the fact that, because it is
a natural product that is not manufactured, natural
slate is low in embodied energy compared with
artificial roofing products. In addition, the lifespan of a
natural slate is two to three times that of fibre-cement,
concrete or clay tile, and natural slate has the potential
for reuse. This means that over its lifespan, a natural
slate roof may have a lesser environmental impact.
The link between embodied energy and whole-life
costs is important and worth considering. Analysis of
lifecycle costs is complicated, as the cost of production
of materials and the energy used to manufacture
them varies continuously. Identification of the energy
embodied in building materials and/or consumed in
operating a building from year to year by heating and
lighting is a simpler matter and so it is possible to
measure and quantify the impact of construction
The embodied energy in buildings that are poorly
managed and insulated can be the equivalent of many
years of the energy required to heat and light the
same building. As energy efficiency standards improve,
less energy is required to heat and light a building and
so the embodied energy of materials used in new
construction becomes more significant as it represents
a greater proportion of the overall energy consumed
or incorporated by a building. This is an important
phenomenon, having been identified only recently,
and is something that will change the nature of
debate and decision-making concerning the reuse of
buildings and energy performance in the years to
A study commissioned by Dublin City Council entitled
Built to Last: The Sustainable Reuse of Buildings (2004)
looked at the lifecycle cost of five buildings and
compared the monetary and environmental cost of
refurbishment versus demolition and reconstruction.
The study found that the construction of new
buildings on brown-field sites was almost always more
expensive than retaining and reusing the existing
buildings. The only exception was where the extent of
building repair and refurbishment required was very
high. The refurbished existing building was also found
to perform better in environmental terms, minimising
the depletion of non-renewable resources being
therefore more sustainable.
The subject of embodied energy is significant and
needs further research. Many factors come into play in
this topic; for example, the performance of traditional
buildings that, for whatever reason, cannot be
insulated; the remaining lifespan of a building; its
architectural heritage significance; the scale of repair
works to be undertaken, and so on. Carbon-emission
evaluations are more measurable than monetary costs,
energy-related returns on investment over a sixty- or a
hundred-year period being very hard to predict.
Upgrading Option
However, there is one clear rule of thumb: the greatest
cost-benefits generally arise from the simplest energyrelated improvements.
For traditional buildings, it is clear that non-intrusive
upgrading measures such as draught proofing, attic or
loft insulation and boiler replacement can ensure that
a traditional building has the potential to out-perform
a newly built building over a lifetime of one hundred
Estimated Payback Period
Cost Bracket
6 months
Lagging to hot water pipework
1 year
Draught proofing windows
and doors
1 year
2 years on average but
dependent on materials used
Less than 8 years
(changing from a 70% to a
90% efficiency boiler would
result in typical savings of
approximately a300 per year)
2 years
Adding front porch
30 years
Installing double glazed windows
40 years
Hot water tank
Upgrading to high-efficiency
boiler with correct controls
Suspended timber floors
Cost and Payback Periods
The energy efficiency improvements indicated above include simple actions such as installing a hot water cylinder
jacket and draught proofing windows. The price and effectiveness of various upgrading measures will vary for any
given building. Available options are discussed in more detail in Chapter 3. This chart gives a rough indication of
typical cost and payback periods for different interventions. These are a guide only and will vary with individual
properties, and will reflect, to a certain extent, the quality of materials and workmanship employed (Source: SEAI)
Conservation principles
In a sense, we look after our historic buildings not only for ourselves but for those
who come after us. Many of these buildings have been around for generations
before us and it is our responsibility to hand them on in good condition to allow
future generations to enjoy them too. So that the works you undertake do not
damage the special qualities of a historic building, it is important to understand
some of the basic principles of good building conservation. Many of these are
common-sense and all are based on an understanding of how old buildings work
and how, with sensitive treatment, they can remain special.
Before you start, learn as much as you can about your particular building. What is
its history? How has it changed over time? Remember that later alterations may be
important too and evidence that the building has been cared for and adapted over
the years with each generation adding its own layer to a unique history.
> Do use the experts - get independent advice from the right people
> Do establish and understand the reasons for failure before undertaking repairs
> Do repair the parts of the building that need it - do not replace them unless
they can no longer do the job they were designed to do
> Do make sure the right materials and repair techniques are used and that even
the smallest changes you make to the building are done well
> Do use techniques that can be easily reversed or undone. This allows for any
unforeseen problems to be corrected in future without damage to the special
qualities of the building
> Do record all repair works for the benefit of future owners
> Don’t overdo it – only do as much work to the building as is necessary, and as
little as possible
> Don’t look at problems in isolation – consider them in the context of the
building as a whole
> Don’t use architectural salvage from elsewhere unless you are certain that the
taking of the materials hasn’t caused the destruction of other old buildings or
been the result of theft
2. Understanding the Building
Fundamental to best practice in building conservation
and in sustainability is a good understanding of the
behaviour and nature of traditional buildings, the
design choices made in their construction and the way
traditional buildings relate to their environment.
The effects of climate
Many early builders were aware of the advantages of
practices such as building in sheltered locations and of
planting trees to form shelter belts. It is therefore
important to acknowledge the impacts of exposure to
both wind and sun, and of latitude and altitude on an
existing building, and to assess how the immediate
setting of the building might be changed to improve
the microclimate in which a building exists.
throughout the country and therefore, the heating
load for different locations varies. The heating load is
the amount a building needs to be heated to reach
the desired internal temperature of 21°C for living
rooms and 18°C for other spaces. When thought of in
terms of an annual amount, this heating load is
expressed as ‘degree days.’ Degree days are a measure
of climatic severity; by virtue of geographic location
alone, there can be a difference of more than 30% in
the heating load on identical buildings in different
locations within Ireland. In effect, a well-insulated
building in one part of the country has a requirement
for heating more than a quarter greater than that of
an identical building in another part of the country.
The need for 21°C as a desirable internal temperature
could be challenged; certainly lower air temperatures
are acceptable where ambient surface temperatures
are relatively high, when people are warmly dressed,
and so on.
A house in the countryside sheltered both by the
local topography and by trees
Ireland has a temperate climate with modest extremes
of minimum and maximum temperatures, whether
considered for individual days, seasons or over an
entire year. The average temperature when taken over
the course of a full year is 10°C. Temperatures tend to
be higher in the south-western areas of the country
and lower in the midlands and north-east. According
to Green Design: Sustainable Building for Ireland, for
every 100m rise above sea level, temperatures drop by
approximately 0.6°C. The difference between the
ambient average external air temperature and a
desired internal, or ‘room’, temperature of 21°C varies
Monthly values for heating degree days
Degree days (or Accumulated Temperature Difference)
are calculated by multiplying the number of degrees
below a base temperature (in Ireland 15.5°C) on any
given day by the number of days in a single year that
the difference occurs. The base temperature of 15.5°C
assumes an internal design temperature of 18.5°C for
an unheated space with a temperature difference
between exterior and interior of 3°C (Source: Green
Design, Sustainable Building for Ireland)
Ireland is an exposed island on the edge of a large
ocean with high maximum and average wind speeds
when compared to most other European countries.
Wind conditions vary from place to place with
pronounced differences on the coast and on high
ground. Winds are strongly influenced by local
topography: for example, rough terrain reduces wind
speed. Similarly trees, vegetation, hills, valleys and
water affect wind speed and, in consequence, the
amount of heat lost from any adjacent buildings.
When wind blows across the external envelope of a
building the rate of heat transfer to or from the
building’s surfaces increases. Wind can also affect heat
gains or losses by infiltration (draughts) due to
increased pressure or through defects in the building
fabric. The importance of achieving shelter from cold
and damp wind has traditionally been understood; the
traditional selection of a location for a dwelling was
often in the lee of a hill and, equally importantly, not in
a hollow prone to frost. Where natural features did not
provide sufficient protection, shelter belts of trees
were often provided.
SW prevaling wind
SW prevaling wind
In terms of orientation, the traditional response was
to orientate houses so that a gable faced the
direction of the prevailing wind, an optimum
arrangement (above). The least effective orientation
for a building, from a thermal efficiency point of
view, is when the main walls are at an angle of 45
degrees to the prevailing wind (below), this is
because the wind streams along the length of the
wall, thereby cooling it, rather than rising over it
Houses on Great Blasket Island in lee of the hill with
their gables turned towards the direction of the
prevailing wind
Creating shelter on a site can reduce heat loss by up to
15% and reduce the wind chill factor for people
outdoors. Notwithstanding any shading they may
confer, a permeable barrier such as a stand of trees is
efficient at reducing wind speed. According to The
Climatic Dwelling - an introduction to climate-responsive
residential architecture, protection by a stand of trees
(with 40-50% permeability) can provide protection for
up to seven or eight times the height of the trees.
Shelter belts with under-planting, positioned
perpendicular to the direction of the prevailing wind,
can offer protection for up to 25 times the height of
the trees provided that the shelter belt is at least 15
times as long as it is high. Interestingly, protection
from a shelter belt also extends upwind for some
distance, as the wind lifts up in advance of passing
over the obstacle ahead of it. In comparison, a solid
wall is only effective for a distance of four to five times
its height (from Green Design, Sustainable Building for
Ireland). Solid obstructions to the wind can also create
uncomfortable and disturbing turbulence whereas
permeable barriers allow some air to move through
the barrier and so create a smoother airflow pattern.
Where they exist, outbuildings can provide shelter to
the main house in addition to providing shelter to the
outdoor working or recreation areas. While it is true
that wind direction constantly changes so that no
single orientation provides a complete solution, when
the direction of the prevailing wind is taken into
account it allows an optimum orientation to be
All the above are approaches to modifying the
microclimate around a building, to the benefit of the
building users, both within and around the building.
The course of the sun is predictable for any given day
of the year. This allows for a full understanding of the
impact of the sun on a building or site. In Ireland,
about 40% of the sun’s radiation is direct and 60%
diffuse, that is, scattered by cloud cover. Harnessing of
the sun’s energy offers huge potential and can be used
effectively for passive and active heating and
Traditional farm complexes were arranged so that
the buildings provided shelter, not only to each
other, but also to the outdoor working areas
Activities within a building, such as cooking,
showering, and clothes and dish-washing, generate
moisture and can raise humidity levels. Even the act of
breathing releases moisture into the air. It is possible
to limit the effects of excessive water-vapour within a
building. Control may relate to simple actions;
solutions such as using well-fitting lids for saucepans
not only save energy in cooking, but also prevent
vapour escaping, which would otherwise condense on
cold surfaces. Ventilating close to the source of
moisture, such as in the shower or over the hob or
sink, is the best solution. However, the impact on a
protected structure or a building within an
architectural conservation area of new external wall
vents requires careful consideration so as to avoid any
adverse impacts; such works may require planning
There is little empirical information available
concerning the impact of humidity or dampness on
overall heat loss, but it is widely understood that
energy is expended in reducing high levels of
humidity and that heat loss is greater when heat
passes through damp materials: damp socks are colder
than dry ones! When humidity is high, comfort levels
can normally be achieved during winter months by
raising the air temperature and during the summer
months by increasing ventilation. Humidity can be
reduced mechanically but dehumidifiers are energyhungry and should be used sparingly. The beneficial
role that traditional finishes such as lime plaster and
timber play in moderating humidity is now being
Sunshine graph: the amount of available sunlight
varies throughout the country (Source: Green
Design: Sustainable Building for Ireland)
The heating season is the period during which the
external temperature drops significantly below
comfortable internal temperatures, requiring some
form of space heating within buildings. In Ireland, the
heating season extends for a period of about 220 to
260 days, from mid autumn through the winter and
into late spring.
Traditionally, the mechanical cooling of buildings has
not been a requirement in Ireland’s temperate climate.
However, cooling sometimes becomes necessary in
office environments, even in traditional buildings,
where the amount of heat generated by electronic
equipment can be substantial, and is usually emitted
during the day when external temperatures are at
their highest. The thermal mass of the traditional
building tends to modify the cooling requirement,
allowing the use of natural ventilation to achieve
comfort levels. In this regard the traditional vertically
sliding sash window offers a highly adjustable solution
to ventilation, its top and bottom opening providing
an optimum arrangement.
During the heating season, heat within a building can
come from a variety of sources. While heating
appliances such as stoves, central heating and open
fires are the main sources, a certain amount of heat is
also gained from electrical appliances, televisions,
computers, washing machines, lighting and indeed
from the occupants of the building.
Solar gain, the heat absorbed by a building from the
sunshine which falls on it, can have a positive impact
on space heating requirements if properly used.
During the heating season while heat is gained from
the sun it is simultaneously being lost through heat
transfer from the interior through the building fabric
and through air infiltration. However, solar gain can be
high for the spring and autumn months which fall
within the heating season, when the sun is low in the
sky and thus able to penetrate further into the interior
of the building through windows. At these times of the
year, solar gain can make a significant difference by
raising internal temperatures and by providing a sense
of comfort through radiant heat.
Short wavelength
radiation from the
sun is transmitted
through the glass
Longer wavelength
radiation is trapped
inside the glass
Planning for warmth
In general, passive design means ensuring that the
fabric of the building and the spaces within it respond
effectively to local climate and site conditions so as to
maintain comfort for the occupants with the minimal
use of energy. In new buildings this can be taken to its
ultimate state where buildings are so well insulated
and sealed against uncontrolled air infiltration that no
heating appliances are required. For a number of
reasons, this is neither achievable, nor indeed
desirable, for traditionally built buildings which need
good ventilation in order to maintain the building
fabric. Nonetheless, it is obvious that past generations
of builders had an inherent understanding of the
thermal behaviour of a building in its setting;
traditional buildings often portray many of the
principles of modern passive design in their location,
orientation and overall design.
Thermal mass of the
wall absorbs and
re-radiates the heat
Solar gain: the ‘greenhouse’ effect. Traditionally,
conservatories and greenhouses were built to
maximise the advantages of the heat from the sun;
sunlight entering through the glass warmed the air
inside allowing for the cultivation of exotic flowers
and fruits. The conservatory also provided a room
for entertaining which was a place of transition
between the house and garden
During daylight hours, buildings gain heat from the
sun through windows. The amount of heat gained
depends on the orientation, time of year, amount of
direct sunlight or cloud cover, the type of glass in the
windows and the nature of the materials within the
building. While, generally speaking, south-facing
windows provide most benefit from the sun, east and
west-facing windows also facilitate large, useful solar
gain. When the sun is low in the sky, during the cooler
seasons and early and late in the day, sunlight
penetrates deeper into the interior of a building,
providing a valuable source of heating energy. When
sunlight falls on a solid internal surface, one with high
thermal mass such as a wall or floor, it heats it. This
heat later radiates back out of the wall or floor,
providing a free source of extra warmth within the
building. Large windows in many traditional buildings
encourage the use of daylight, reducing the need for
artificial lighting. Arising from this, it is clear that the
overall shape and design of a building determine the
extent to which its occupants benefit from solar gain.
In order to use solar gain to its full advantage, room
uses and activities should correspond to periods of
sunshine; generally bedrooms and kitchens should
face east to benefit from the morning sun and living
rooms and dining rooms west, for evening use. In
larger houses, where the possibility of choice exists,
cooler north-facing rooms could be used primarily
during the summer. Appropriate use of space is also
important. Peripheral spaces can be left unheated (or
with minimal heating) and unused during the colder
months of the year; unheated conservatories and
sunrooms fall into this category. Where there is an
existing conservatory it should be left unheated and
preferably thermally separated from the main house
with a door.
Trinity College Library, Dublin. There were never
fireplaces in the library, to avoid the risk of fire
breaking out. Sunlight streams in through large
single-glazed south-facing windows, maximising
solar gain. Appropriate steps should be taken to
protect light-sensitive historic furnishings and
contents from damage caused by both ultra-violet
light and visible sunlight
In general, the greater the area of exposed surface a
building has, the greater the amount of heat loss that
occurs. Physically attaching buildings one to the other
is therefore immediately advantageous, as the area of
wall exposed to the elements is significantly reduced,
notionally by about a half in a terraced building, and
by about a quarter in a semi-detached one.
bedroom bedroom
living room living room
The floor plan of a pair of rural cottages shows, in
red, a newly constructed, well-insulated, northfacing extension housing bathrooms and
bedrooms and, in yellow, south-facing sunrooms to
take advantage of solar gain and provide heat and
light to the living rooms behind
Building use
In addition to all of the above, the way people
perceive the comfort of a building is dependent on
the building’s use, the activities of its users and the
nature of its interior furnishings.
The extent to which a building is used, and the pattern
of that usage, changes its energy requirements. Take,
for example, two identical houses: one with a young
family who occupies the house during the day and the
other with a single person who is out at work all day.
The required space heating varies greatly between the
two buildings. Similarly, buildings used for domestic
and commercial purposes produce very different
amounts of heat. Therefore, the heating solutions for
buildings should reflect an understanding of the
patterns of use of the building. In addition, the
number of appliances being run in a building has an
impact on the space heating requirements. In a
commercial building, the heat generated by
computers and artificial lighting reduces the amount
of heat to be provided by a heating system,
sometimes resulting in a requirement for cooling. A
domestic home with a large family running a number
of heat-generating appliances, such as personal
computers, televisions, computer games and washing
machines, requires less space heating than a house
with a single occupant, running fewer appliances.
Within the internal environment of a building there
can be many reasons for a person’s body temperature
to change. These reasons can be broken down into
two main factors: environmental and personal.
Environmental factors include air temperature, the
Leather linings and tapestries line the walls of this room and improve the thermal comfort of the occupants
Heat loss from buildings
Heat is lost from the interior of a building in two main
ways: by transfer through the materials that make up
the external envelope of the building (measured as a
U-value) or by the exchange of air between the
interior and the exterior environment that is,
It is estimated that typical heat losses from a building
are as follows:
> Walls 35%
> Roofs 25%
> Floors 15%
> Draughts 15%
> Windows 10%
Box pews were the traditional way of keeping
church-goers warm in an unheated, or poorly
heated, church. The timber floor to each pew
provided a warm surface underfoot, while the ‘box’
protected its occupants from draughts
temperature radiated by the surrounding building
fabric, air movement and humidity. Personal factors
include clothing, activity level, body weight and age:
new-born infants and elderly people generally require
greater warmth.
Preventing loss of heat and excessive air movement
helps maintain a comfortable internal air temperature.
The temperature of the interior surfaces within a room
is as important as the temperature of the air within a
room. Colder surfaces such as stone walls, stone or tile
floors and glass which are slow to heat up can give the
perception of a cold environment, leading to a feeling
of discomfort. Traditionally, these problems were
overcome with curtains, tapestries, wallpaper and
timber panelling. Similar solutions are still applicable
today, perhaps even on a seasonal basis. The use of
folding screens within a large room, or even the use of
more permanent linings can be considered where
appropriate. The installation of permanent linings in a
protected structure may require planning permission.
Heat transfer through building
The rate at which heat is transferred through the
external envelope of a building is expressed as a Uvalue. Heat always flows from a warm area to a cold
area and each material component of the external
envelope of a building transfers heat at different rates.
The slower a material transfers heat, the better it is as
an insulator. Low U-values are given to those materials
that transfer heat slowly and are therefore good
insulators; thus lower U-values are better. For any
given construction, independent of U-value, heat loss
is also directly related to the temperature difference
between the exterior and interior, and, to a lesser
degree, the colour and texture of the external walls.
Moisture reduces any material’s ability to insulate, as
the conductivity of material increases when damp and
with it the U-value; even moderate changes in
dampness can significantly increase an element’s
U-value, reducing its insulating properties. Common
causes of moisture ingress include damp penetration
in walls due to defective or removed render, leaking
gutters and poorly fitting windows frames. It is
therefore important to ensure that buildings are well
maintained and weather-proofed to achieve low
Calculating U-values
This process requires some technical know-how. An owner rarely needs to be able
to calculate U-values for a building but it may be useful to understand the process
and how it might be applicable to works that are undertaken to improve energy
The first step is to establish the thermal conductivity k (W/mK) of each material in
the construction: this is done by reference to published tables. Next calculate the
thermal resistance R (m²K/W) for each material as follows:
R = –kt (m²K/W)
where t is the thickness of each material.
The U-value of a building element made of multiple layers is given by:
U = (R + R + R + ... + R ) (W/m²K)
As U-values are calculated based on a notional fixed temperature difference
between inside and outside, they remain constant for a given type and thickness of
material; the U-value does not normally take into account orientation or exposure,
although a refined evaluation of overall heat losses for windows gives radically different values depending on whether a window is north or south facing.
While overall heat loss calculations can be adjusted for emissivity (the extent to
which a body reflects or radiates heat) of the internal and external surfaces, it is
more difficult to adjust calculations for material defects or climate variations (such
as a chilling wind), both of which increase the rate at which heat is lost through a
building’s shell.
Tables giving U-values for common construction types are available from the
Sustainable Energy Authority of Ireland (SEAI). Simple software for calculating
U-values is also available. Manufacturers of insulating products normally indicate
the U-value on the product literature. However, this data must be verifiable if it is to
be used in calculations. The appropriate European Standard or keymark (for example BSI) should also appear on the literature to enable traceability.
U-values for works governed by the Building Regulations in existing buildings can
be found in Technical Guidance Document L of the Regulations.
Thermal bridging
Thermal bridging, also known as ‘cold bridging’, occurs
at locations where part of an external wall, floor or
roof, draws heat directly to the outside at a faster rate
than surrounding materials. In the interior, these
thermal bridges are cooler than the surrounding
building material and therefore attract condensation,
often leading to mould growth. Any proposed
insulation works should ensure that all parts of a room
are insulated consistently to avoid thermal bridging. It
should be noted that higher insulation levels can
exacerbate issues related to thermal bridging as the
temperature difference between the insulated areas
and any remaining thermal bridges will be greater,
allowing a concentration of condensing moisture to
occur on the thermal bridge.
This plastered ceiling has no insulation above it.
Discolouration can be seen on the plasterwork
between the timber joists located above, as the
timber is slower to transfer heat to the cold roof
space than the plaster alone. Dust particles in the
warm air passing through the plaster remain
trapped on the surface causing the discolouration
Ventilation and indoor air
All buildings require ventilation but traditional
buildings require somewhat higher rates of ventilation
than modern construction. Ventilation allows the
moist air produced by the occupants themselves through expiration, by cooking, by bathing and
showering and domestic washing - to escape before it
causes harm to the building fabric and furnishings.
Ventilation also plays an important role with regard to
the health of the occupants, ridding buildings of
indoor air pollution associated with health problems
including allergies, asthma, infectious diseases and
‘sick building syndrome.’ Many indoor air pollutants
are thought to be the result of increased use of
solvents, cleaning agents, office appliances and the
like. Ideally, there should be a regular purge ventilation
of the air within buildings, opening windows fully for
about ten minutes a day where possible. Rooms with
open fires and open-flue appliances must have a
sufficient air supply to avoid a dangerous build-up of
carbon monoxide. Where draught-proofing
programmes are proposed this must be taken into
consideration. Installing new vents may have
implications for the external appearance of the
building. It requires careful consideration to avoid
adverse impacts, and may require planning
In modern buildings, ventilation is generally controlled
to some extent; extraction fans in kitchens and
bathrooms remove moisture at the source of its
production while ‘trickle ventilation’ through window
and wall vents allows a steady but controllable
ventilation flow. In traditional buildings, ventilation
comes from a variety of sources, with air being
admitted down open chimney flues, through roofs and
at the edges of doors and windows.
While all buildings require some level of ventilation,
traditional buildings require ventilation for one further
and very important reason. Solid walls were generally
constructed using soft porous and breathable
materials that absorb and release moisture on a
cyclical basis, becoming damp during wet weather
and drying out when conditions are finer. Traditionally,
moisture which migrated through the full depth of a
wall was dissipated by the high levels of ventilation
created by the use of open fires which drew air into
the building and out through the chimneys. Where
this ventilation flow is significantly reduced by the
sealing up of flues and windows, or by the use of
dense cement or plastic-based impermeable coatings
to walls, damp conditions can develop, with the
potential for mould and fungal growth to flourish. In
addition to being unsightly, high levels of mould
growth can cause or aggravate respiratory illnesses
particularly in the young and elderly. If the lack of
ventilation is allowed to continue unchecked, it will
increase the risk of dangerous levels of moisture
building up in structural timbers, making them
vulnerable to fungal and/or insect attack and will lead
to deterioration of internal finishes, necessitating
redecoration. It is therefore important that any
alterations to a traditional building provide for the
continuing ventilation of the building fabric to the
necessary levels.
Heat lost by ventilation
through the open flue
Ventilation through the
permeable roof covering
Roof ventilation
Heat gains from lighting
Heating from an open fire
Heat gains from
the occupants
Open fire draws air in
through gaps in the
window frames
Ventilation through
an open fire
Ventilation to remove
moisture produced in
Wind and sun dry out
the walls
Porous walls absorb
Heat gains from
cooking and electrical
Moisture evaporates
from permeable walls
Moisture absorbed from
the ground is dissipated
by ventilation
A comparison of the ventilation and heating requirements for a traditional building (above)
and a modern building (below)
Roof ventilation
Heat gains from
Trickle ventilation
through window frames
Heat gains from the
Heating from
Extractor fan expels
moisture and air resulting in
ventilation and heat loss
External finish repels
Heat gains from
cooking and electrical
Damp-proof membrane under the
floor and damp-proof courses in
the walls repel ground moisture
Thermal mass
Different materials absorb and radiate heat at different
rates. Thermal mass is the ability of high-density
materials such as brick and stone to absorb heat,
retain it and then release it again slowly over time,
helping to moderate the temperature fluctuations
within a room. Thermal inertia is the term used to
describe this process. A thermally lightweight
structure responds very quickly to solar gain or central
heating and is less effective in storing free energy for
use later, and can result in larger temperature swings
within a room.
Depending on the orientation and size of the windows
in a building, the use of passive solar gain is improved
in buildings that have a high thermal mass, arising
from their overall construction; for example masonry
internal and external walls and solid floors allow a
building to absorb, retain and later release the heat
absorbed from the sun. The possibility of effectively
exploiting solar gain in a building of high thermal
mass is optimised if a building is occupied during
daylight hours, when the occupants can take full
advantage of the free stored heat.
It should be noted that a heavy masonry wall and a
well-insulated lightweight structure with the same
U-value (rate of heat loss) have very different
responses to internal space heating. It may well be
suitable that a building should respond quickly to heat
or cold, but in general it is accepted that for traditional
buildings high thermal mass and a relatively slow
response time are advantageous.
While traditional buildings tend to have high thermal
mass, their occupants frequently fail to exploit this
potential as the buildings may be uninsulated and
draughty. However, when one addresses these
shortcomings, traditional buildings can have desirable
qualities and can efficiently provide comfort and
warmth for their occupants.
Same U-value
Low Thermal Capacity
High Thermal Capacity
Two different wall constructions (above) with similar U-values may have very different thermal masses
Internal temperature with low thermal mass
temperature range
Internal temperature with high thermal mass
External temperature
A graph (above) showing the temperature changes within buildings with high thermal mass (red line) and with low
thermal mass (yellow line). As can be seen by the red line, less extreme changes of temperature are experienced
inside the building with the higher thermal mass
A medieval tower
house with thick
stone walls and a
high thermal mass
(above) and an
lightweight timber
building with low
thermal mass
Assessment methods
There are a number of non-destructive techniques
available to assess the energy efficiency of an existing
building. These range from the use of simple handheld devices such as moisture meters and borescopes
to more complex and expensive methods such as
thermal imaging. Expert knowledge and experience
will be needed to decide which assessment method is
appropriate in a particular case, to undertake the
assessment and to interpret the results.
Thermography, or thermal imaging, is photography
using a camera that captures infra-red (IR) light rather
than the visible light captured by a standard camera. IR
light occurs beyond the red end of the visible light
spectrum and is invisible to the naked eye. All objects
that are warmer than absolute zero (-273°C) emit IR
light. The warmer the object is, the more IR light it
emits. IR cameras record the amount of IR light emitted
by an object and translate it into a temperature which
is indicated on a scale bar adjacent to the thermal
image or thermogram. Even very small temperature
differences, as low as 0.1°C, can be recorded by IR
cameras. The image produced by an IR camera is multicoloured with each colour representing a different
temperature. Different colour scales can be used
depending on the objects photographed.
Thermography has many varied applications in
different disciplines and can be a useful tool when
assessing the condition of a building. It has particular
advantages for investigating historic buildings as it is a
non-invasive, non-destructive method.
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A thermographic image of a double-glazed door at
semi-basement level in a nineteenth-century
terraced house; note how the yellow patches at the
base of the wall, which are damper, indicate that
these areas are emitting heat at a higher rate than
the rest of the wall
Thermal imaging can be used to identify potential
problems with a building’s fabric. When looking at
traditional buildings, thermal imaging might be used
to identify areas of dampness and to locate thinner
depths of wall, cracking and voids. Expertise is
required both in deciding how and when to take IR
images and later in interpreting the information. For
example, objects which have high or low emissivity
such as metal do not give an accurate temperature
reading. Weather conditions, orientation and the time
of day when the image was taken all have the
potential to affect the reading. The information
gathered from thermal images can be properly
assessed only in conjunction with data gathered as
part of a comprehensive condition survey.
Air-pressure testing, or fan-pressurisation testing,
assesses the air-tightness of a building and the rate of
air leakage occurring through the fabric. Modern
building methods seek to ‘build tight and ventilate
right.’ However, as discussed elsewhere in this booklet,
this maxim is not appropriate for traditional buildings
which require relatively high levels of natural
ventilation to keep the building fabric in good
condition. Nonetheless, testing a building’s airtightness may highlight areas or points of particularly
high air leakage which could be remedied without
compromising the health of the building fabric. Care
should be taken when undertaking air-pressure tests
on older buildings which contain fragile building
elements, including delicate glazing bars and thin,
hand-made panes of glass which would be damaged if
subjected to excessive pressure.
Inspections of concealed parts of a building’s
construction can be carried out using a borescope or
fibrescope, generally with minimal disruption to the
building. This type of inspection can be used to
investigate walls, roofs and floors for hidden defects by
inserting a borescope or fibrescope into a small
inspection hole. In the interior of a protected structure,
the drilling of an inspection hole should be carried out
with care and a location chosen that avoids any
adverse impacts. In some cases, drilling through the
building fabric may be unacceptable.
Such an inspection can be used as a follow-up to a
thermographic survey to investigate the exact cause
of heat loss through a particular part of the building
fabric. The results of the inspection can be
photographed or videoed on a camera attached to the
Electrical moisture meters can be useful in detecting
the presence of moisture in building fabric. Simple
electrical resistance meters are relatively cheap, easy
to use and widely available. However, the results can
be inaccurate and misleading. False, elevated readings
can be obtained, for example, where there are
concentrations of salts on the surface of a wall, foil
behind plasterboard, condensation and the like.
Moisture meters are most useful and reliable when
used on timber.
Ultrasonic scanning involves the use of high-frequency
sound waves to provide a cross-section through a
material. It can be used across very fragile surfaces
without causing damage which makes it particularly
suited to use on sensitive historic buildings. This nondestructive technique can be used in the investigation
of timbers to determine if there is any decay present
and, if so, its extent. It can also be used to assess the
structural integrity of timber joints and the presence
of zones of weakness within stone blocks. A high level
of skill and experience is needed to carry out the
assessment and interpret the results.
Building Energy Rating (BER)
and traditional buildings
While the results need to be treated with caution,
some useful information can be obtained from the use
of a moisture meter. A number of readings taken
across a surface can give a pattern of moisture levels.
Localised high readings in the middle of a wall may
indicate a building defect that has allowed rainwater
Other assessment methods are available which
include the measurement of U-values (the rate of heat
transfer through a material) on site using a
combination of thermography and a heat flux meter.
There are international standards for making these site
measurements. This is an expensive and complex
assessment method that requires considerable
expertise both to undertake and to analyse the
resulting data.
Examination of a building with radar uses low-power
radio pulses to determine the make-up and condition
of a structure. It can be used successfully on most
construction materials to locate and measure voids,
cracks, areas of corrosion and discontinuities in walls
or floors and to detect the presence of old chimney
flues. As with in-situ U-value measuring, the use of
radar is a relatively expensive and complex assessment
method that requires expertise to undertake and to
analyse the resulting data.
Sample Building Energy Rating Certificate for
dwellings. The most energy efficient rating is ‘A1’
(green) down to the least efficient is ‘G’ (red)
The European Directive on the Energy Performance of
Buildings promotes energy efficiency in all buildings
within the European Union. One of its requirements is
that all new and existing buildings within the EU have
an energy performance certificate. The implementation
of performance certificates in Ireland is managed by
the Sustainable Energy Authority of Ireland (SEAI) and
takes the form of Building Energy Ratings (BER) for all
building types, calculated by the Domestic Energy
Assessment Procedure (DEAP) for dwellings and by the
Non-domestic Energy Assessment Procedure (NEAP)
for other building types. Public buildings greater than
1000m2 are also required to have Display Energy
BER certificates are now required for all new buildings
and, in the case of existing buildings, for premises
undergoing transaction, whether lease or sale. While
buildings protected under the National Monuments
Acts, protected structures and proposed protected
structures are exempt from the requirements to have a
BER, all other traditionally built buildings are required
to have a BER certificate when let or sold. There is no
requirement that a building achieve a particular rating.
The BER assesses the energy performance of the
building, allowing potential buyers and tenants to take
energy performance into consideration in their
decision to purchase or rent a property.
Following assessment of the building by a trained
assessor, a certificate is prepared and issued to the
building owner. The energy rating displays both the
energy requirement of the building in terms of
‘primary energy’ and the resultant carbon dioxide
emissions. Normally a building owner thinks in terms
of ‘delivered energy.’ Delivered energy corresponds to
the energy consumption that would normally appear
on the energy bills of the building. Primary energy
includes delivered energy, plus an allowance for the
energy ‘overhead’ incurred in extracting, processing
and transporting a fuel or other energy carrier to the
The objective of BER is to provide an energy rating for
buildings, expressed in a familiar form similar to that
used for energy-rated domestic appliances such as
fridges, based on a standard system of appraisal which
allows all properties to be compared regardless of
how they are used or occupied. In the assessment
methodology, the size and shape of a building are
taken into account and its floor area determines the
number of occupants that are assumed. The rating is
based on a standardised heating schedule of a typical
household, assuming two hours heating in the
morning and six in the evening. A building’s BER does
not take into account its location within the country
(whether in the colder north or warmer south) but
does consider orientation relative to the sun. It is also
important to bear in mind that it does not take into
account an individual household’s energy usage but
assumes a standardised usage.
At present, the standard calculation for older buildings
relies on default values for heat loss calculations. These
defaults are conservative and at times may poorly
represent an older building’s ability to retain heat. For
example, there is only one figure for all types of stone,
whereas in reality different stone types lose heat at
different rates. Embodied energy is currently not
accounted for in the BER system; this is an issue that
requires more research in order that the characteristics
of historic buildings in energy terms may be fully
appreciated and recognised.
On completion of a BER calculation for an existing
building, the assessment software generates a list of
recommendations for upgrading the building in the
form of an advisory report. These recommendations
have been generally designed for existing buildings of
modern construction rather than traditionally built
buildings. As the BER assessor is responsible for
deciding which recommendations are appropriate for
a particular property, it is important to ensure that the
assessor understands how traditional buildings
perform, as inappropriate recommendations could
lead to damage of older building fabric. A building
conservation expert should be consulted prior to
undertaking any recommendations on foot of a BER
Getting the right advice
When it comes to carrying out works to a traditional building, regardless of its age or size, it is important to
know when specialist advice is needed and where to find the right help. It is a false economy not to get the
best advice before undertaking any works. Ill-considered upgrading works can damage a building in the
long-term, devalue your property and may be difficult and expensive to undo.
You will need the right advice for the particular job. Sometimes you will require an architect, a surveyor or a
structural engineer. You should ensure that any advisor is independent and objective, not someone trying to
sell you something or with a vested interest in increasing the scale and expense of work. You need someone
who understands old buildings, has experience in dealing with them and has trained to work with them. He
or she should be knowledgeable and experienced in dealing with your type of building. Many building
professionals and contractors are only involved with modern construction and may not know how to deal
sympathetically with a traditional building. Do not choose a person or company based on cost alone. The
cheapest quote you receive may be from the person who does not fully understand the complexity of the
The interpretation and application of the more technical recommendations in this guide should be entrusted
to suitably qualified and competent persons. When employing a professional advisor or a building
contractor, check their qualifications and status with the relevant bodies and institutes first. Ask for
references and for the locations and photographs of recent similar work undertaken. Do not be afraid to
follow up the references and to visit other building projects. A good practitioner won’t mind you doing this. If
you see a good job successfully completed on a similar building to yours, find out who did the work, whether
they would be suitable for the works you want to undertake and if the building owner was satisfied.
Be clear when briefing your advisor what you want him or her to do. A good advisor should be able to
undertake an inspection of your property, recommend options for upgrading its energy efficiency, specify
the work required, get a firm price from a suitable builder and oversee the work on site as it progresses. If
your building is likely to need ongoing conservation and repair works over a number of years, your
relationship with your advisor and builder will be important both to you and your building and continuity
will be a great advantage. They will be able to become familiar with the property and to understand how it
acts and will build up expertise based on your particular building.
The Royal Institute of the Architects of Ireland keeps a register of architects accredited in building
conservation and will be able to provide you with a list. Similarly, the Society of Chartered Surveyors has a
register of conservation surveyors. The Construction Industry Federation has a register of heritage
contractors. The architectural conservation officer in your local authority may have information on suitable
professionals, building contractors or suppliers in your area.
3. Upgrading the Building
Upgrading a building to improve its energy efficiency
requires careful consideration if works are to be
effective, economical and avoid damaging the historic
character of the building.
Building management
The first step should be to consider how the building
is used and managed. The greatest savings in energy
consumption generally come from changing the way a
building is used and the behaviour of its occupants.
Some relatively simple measures can result in
immediate benefits including:
> Turning down thermostats by as little as 1ºC (this
can result in potential savings of 5-10% on a fuel
> Having shorter or more efficient running times for
the heating system
Building condition
The next step should be to consider whether or not
the building is in a good state of repair: there is often
little point in insulating or draught proofing if it is not.
Generally dry buildings are warmer buildings: high
moisture levels in the fabric of a building resulting
from leaks or general dampness seriously reduce a
building’s thermal efficiency. A wet wall transfers heat
from the interior of a building about 40% more quickly
than a dry wall, resulting in much greater heat loss. It is
therefore important to ensure that roofs, gutters and
downpipes are well maintained. Similarly, soil banked
up against a wall and the use of dense, impermeable
cement renders can trap moisture in walls. Therefore,
before embarking on upgrading works, the condition
of the building should be inspected and any necessary
maintenance and repair works completed. For further
information, see Maintenance: a guide to the care of
older buildings in this Advice Series.
> Heating unused or seldom-used rooms only to a
level sufficient to avoid mustiness and mould
growth and keeping the doors to such rooms
> Using energy-efficient light bulbs
> Placing fridges and freezers in cooler rooms where
they will consume less electricity
> Closing shutters and curtains at night
> Fitting smart meters to provide information on
electricity usage and raise awareness of energy
> Ensuring that the correct use of heating controls is
understood by the occupants on completion of
any upgrading works and that instructions are
passed over to the new owner when the building
changes hands. A lack of understanding of the
controls for a heating system can lead to significant inefficiencies in the use of fuel and energy
> Using daylight for lighting rather than artificial
SEAI and some energy providers provide details on
further energy saving measures on their websites.
The importance of maintaining rainwater goods in
good working order cannot be over-emphasised.
Not only will the water running down this wall
cause rotting of the building fabric and damage to
the interior in the short to medium term; the
dampness in the wall will also cause it to transmit
heat more quickly from the inside of the building
making it colder and less thermally efficient
Preliminaries to upgrading
> Assess which elements of the building require
upgrading works and complete a list of proposed
works. Based on this list, estimate the cost of
upgrading and the potential energy savings that
will result on completion of the works. Be clear as
to the purpose of the works: is it to save money, to
reduce the building’s carbon footprint, or to
improve comfort levels?
> Consider the effect of any proposed works on the
appearance of the exterior and interior of a building and ensure that no works will interfere with, or
damage, important elements or decorative finishes
or the historic character of the building as a whole
> Bear in mind that the cheapest works with the
greatest energy savings are draught proofing, attic
insulation and upgrading the boiler and heating
controls. These can often be carried out with a
minimal impact on the appearance of a building or
its historic fabric, although certain caveats apply
> If works are to be undertaken on a phased basis
consider targeting colder rooms first, such as
north-facing rooms
> Don’t reduce ventilation too much; ventilation is
needed for human comfort and to dispel moisture
within a traditionally built building
Products and materials
Before any new materials are introduced into a historic
building, they should be proven to work, ideally having
been in use in Ireland for 25 years or more and be
known to perform well and not to have any damaging
effects on historic fabric. However, with the
development of more environmentally friendly
products in recent years, in response to a growing
awareness of the negative aspects of many commonly
used building materials, it is possible that there are
superior products available which are both durable
and environmentally sustainable and which have not
been tested over a long period of time. Expert advice
from a building professional specialising in historic
building conservation will be required prior to
specifying and using innovative products, as a full
understanding of their characteristics, qualities,
limitations and appropriate application is necessary.
Untried and untested materials should not generally
be used in a historic building. If their use is not
possible to avoid, then it is important that they should
be fully reversible, that is, that they can be removed at
a later stage if problems arise without causing any
damage to the historic fabric of the building.
It is important to ensure that any new materials
introduced into the building comply with all relevant
standards or have third party certification as to their
suitability, such as NSAI Agrément Certificates.
Performance issues relating to fire resistance, moisture
ingress and infestation should be properly considered.
Many upgrading options involve the use of insulation.
In choosing which insulation material to use the
following should be considered:
> Research all proposed insulation materials. There is
a large variety of insulating materials available,
many of which provide the same insulation properties but vary in price and material content.
Materials which meet sustainability criteria should
be identified: some artificial or plastic-based insulation materials may embody substantial amounts
of energy. Account should be taken of the expected lifespan of the material and whether or not
there are available alternative materials.
Additionally, health aspects related to off-gassing
(gases exuded by some materials), compaction
over time, and the ‘breathability’ of the materials
themselves need to be taken into consideration
> In order to protect the character of buildings of
architectural and historic interest, it is generally
not appropriate to insulate masonry walls, because
of the impact on an interior of dry lining or plastering, or on the appearance of an exterior through
the use of external insulation systems, together
with the difficulties of successfully detailing joints
such as at eaves and windows sills
> Any proposed insulation works should ensure that
all parts of a room are insulated consistently to avoid
thermal bridging. Higher insulation levels can exacerbate problems associated with thermal bridging
> When choosing products, consider the results
which can be obtained from different options in
terms of both the financial investment and resultant energy savings
> Quilt insulation can be in the form of mineral wool,
sheep’s wool or hemp. Mineral wool may compress
and sag over time if it gets damp and is unpleasant to handle. Sheep’s wool and hemp are
advantageous as both allow any moisture which is
absorbed to later evaporate: this means that these
materials are less prone to compression in the long
term. Wool, being a natural material and a by-product of the agricultural industry, can be seen to be
environmentally friendly in itself, while hemp is a
carbon-negative material, that is, it absorbs carbon
as it grows and locks it away in the plant
> Blown insulation, often made up of recycled paper
and also known as cellulose, can be blown into
spaces such as attics up to the desired level of
insulation. However, care should be taken to
ensure that all vents or ventilation routes remain
unblocked when filling spaces with this type of
insulation. Reducing levels of ventilation can result
in damaging levels of moisture content building
up in the roof timbers
> While sheep’s wool, hemp and blown insulation
materials appear to be better on health and environmental grounds, their introduction is relatively
recent and accordingly issues related to their use
may not yet have been fully identified. Certification
by independent, third party bodies, such as the
NSAI, should ensure that the product chosen is
suitable for use and will provide appropriate guidance for installation.
Upgrading works and health and safety issues
When commissioning or carrying out improvement works within an older structure, the building owner should be aware of the requirements set out in the Safety,
Health and Welfare at Work Act 2005, the Safety, Health and Welfare at Work
(Construction) Regulations 2006 and the Safety, Health and Welfare at Work
(Exposure to Asbestos) Regulations 2006. Helpful guidance is provided on the
Health and Safety Authority website
Before embarking on works to improve the thermal efficiency of any property the
following safety considerations should be taken into account:
> Older buildings may contain hazardous materials that could be dangerous to a
person’s health such as asbestos or other contaminants. Asbestos can be found
within man-made roof coverings, lagging on pipework, older sheet or tile
flooring materials, WC cisterns and seats and other building components. In the
course of general upgrading works interference with, or breakage of, such
materials must comply with the requirements of current legislation and in
certain cases must be removed by specialist licensed contractors. Professional
advice should be sought to identify and remove such materials.
> Certain materials such as fibreglass or mineral wool insulation should be
handled carefully using gloves, masks, eye goggles and other protective
garments to prevent harm caused either by inhalation or physical contact with
the small fibres that make up the material, particularly as such materials are
often fitted in attics and other poorly ventilated spaces.
> There are serious health risks associated with lead paints where a painted
surface is flaking or chipping or where it is disturbed. For absolute certainty as
to the presence of lead paint, specialist laboratory testing should first be
carried out.
Reducing draughts
In traditional buildings, heat loss commonly occurs as
a result of excessive ventilation or draughts. Over time
buildings move, settle and shrink causing gaps to
open up in locations where there were none originally.
This often happens at the junction between windows
and their surrounding masonry, or between sashes
and window frames, including shutter boxes. Previous
alterations to the building and works to install or
remove services may have left gaps and cracks that
were never properly sealed. Localised decay may have
resulted in gaps particularly around doors and
windows. All these factors invariably result in increased
levels of ventilation and draughts, resulting in
discomfort for the building users as well as the loss of
Measures to reduce draughts should be given careful
consideration both on a room-by-room basis and in
the context of the building as a whole. Consideration
should be given to reducing excessive air flow
through, and around, particular elements in a building.
It may be possible to draught proof windows in rooms
which have other sources of ventilation such as wall
vents and open chimney flues. Windows in rooms with
no other vents can be partially draught proofed but a
strip of draught proofing should always be omitted,
such as at the meeting rails of sash windows, to ensure
continued ventilation. If this does not provide
sufficient ventilation in a particular situation, the top
sash could be fixed in an open position to provide a
small gap, allowing trickle movement of air to circulate
from the meeting rail to the top. The top sash can be
secured in place with a block on the window frame
and both the top and bottom sash should be locked
into the side of the frame, as a lock at the meeting rail
will not be usable.
Inflatable chimney balloons can be used to seal open
chimney flues that are not in use. These have the
advantage that, if their presence is forgotten and a fire
is lit, they deflate and melt away within a very short
period. Fully sealing a flue is not recommended.
Sufficient ventilation is needed in the interior to keep
the building fabric in good condition and for the
health of the occupants. In addition, ventilation is
needed within the flue itself to allow any rainwater
that enters the flue to evaporate; otherwise it might
combine with the combustion products in the flue to
create acidic conditions. Where it is proposed to install
a chimney balloon it may be possible to insert an
open pipe into the flue before inflating the balloon so
that a sufficient passage of air is maintained between
the room and the outside air, via the flue.
In rooms such as kitchens and utility rooms that
require additional ventilation because of the presence
of heat and vapour-producing appliances, mechanical
ventilation should be provided to remove the
moisture from the interior of the building before it
causes damage. Where possible, unused chimneys can
be employed in lieu of vents in the wall to provide
mechanical or passive ventilation. The installation of
new vents in external walls requires careful
consideration and possibly planning permission.
An estimated 25% of heat loss occurs through a
building’s roof. The scope for reducing heat loss from a
historic building in a non-intrusive way is greatest at
attic and roof level; fitting insulation at roof level can
be one of the most cost-effective measures in
improving thermal performance in a traditional
Both pitched and flat roofs in traditional buildings
were generally constructed of timber structural
elements. Flat roofs were traditionally covered with
lead or copper, which are high-quality, long-lasting
cladding materials. Older pitched roofs are generally
covered with natural slate or tiles although some may
originally have been thatched. Thatched roofs are
comparatively rare today, although many more
probably survive unseen under later corrugated iron
roof coverings. Thatch, by its nature, is an excellent
insulant and thatched roofs generally do not require
the addition of insulation and in fact may deteriorate if
inappropriately lined from below. For further
information, see Roofs – a guide to the repair of historic
roofs and Thatch – a guide to the repair of thatched roofs
in this Advice Series.
Traditional buildings were not fitted with attic
insulation at the time of their construction. Many have
been upgraded since but there may be scope for
improving the existing insulation levels in many
buildings. Where no attic insulation is present, the
fitting of it is an easy and cost-effective way to
improve a building’s thermal insulation. Existing
insulation can be left in place and added to, provided
that it is dry. Damp insulation should be removed as it
is no longer acting as an insulating layer. The cause of
the damp should be investigated and dealt with
before new insulation is installed.
The fitting of insulation should have no adverse effects
on a traditional building provided that ventilation and
moisture control are properly addressed. Necessary
repair works for leaks or timber treatment for rot or
insect attack should be completed prior to
commencing any upgrading of insulation levels.
Condensation on roof timbers or on the underside of a
roof covering (on the backs of slates or on the
underside of lead sheeting) indicates inadequate
ventilation and this should be addressed prior to
proceeding with any further insulating works.
It makes sense to install the maximum thickness of
insulation possible in the space available without
compromising the ventilation of the roof space.
Ventilation is very important in roof spaces as it
prevents insect attack and fungal decay in the roof
timbers by moderating humidity and the moisture
content of the timber. Prior to commencing any loft
insulation, it is important to establish the location of
the vents, if these exist, and to verify that they will not
become blocked by any added insulation. Where
actual vents do not exist, a sufficient amount of
ventilation probably occurs at gaps at the eaves of the
roof and in such cases, the insulation should be fitted
so as to ensure a through flow of air under the eaves
and into the roof space is maintained. While adding
insulation to a roof space does not normally require
any planning permission, additional roof vents may
require permission, where the building is a protected
structure or is located in an architectural conservation
Insulation should be fitted tightly between the joists
or rafters as any gaps will compromise the insulation's
effectiveness. Quilt or blown insulation compress to fit
into the spaces to which they are added while specific
rigid insulation has been developed for roofs with
grooves cut into the board to allow it to be
compressed between rafters and joists, thus reducing
the potential for gaps if the board is not cut correctly.
A large roof space with no insulation above the
ceiling; while the heat rising from the building
interior may benefit the timber and other building
materials in the roof space, a lot of energy is
wasted in this way
Attic and loft spaces within pitched roofs which are to
be unheated can be insulated at floor level. If the attic
is in use as a habitable space, insulation should be
fitted above, between the rafters. A loft space can be
insulated using quilt insulation. Where there is
insufficient depth between the existing ceiling joists
an additional layer of insulation can be laid on top to
increase the total thickness. If the attic is not floored
out for storage purposes, it is enough to lay the
insulation between and on top of the existing joists,
with provision for secure access to water tanks, and
the like. It is particularly important to ensure that any
access hatch to the attic or loft is well-fitting and
insulated on the attic side.
It should be noted that many historic buildings,
particularly those constructed in the eighteenth and
early-nineteenth centuries, have relatively
insubstantial roof and ceiling construction, relying on
slight timbers configured in a particular way. Use of
such attics for storage must take account of the
structural strength of the existing timbers, with an
awareness that damage can be caused to lath-andplaster ceilings by deflection of the supporting joists. If
storage is required in the loft space a careful structural
analysis should first be undertaken to ensure there
would be no resulting damage.
Uninsulated space
beneath the water tank
Insulation laid between
the ceiling joists
Insulation wrapped
around the water tank
Rigid insulation to coved section of ceiling
with 50mm gap left for ventilation
Quilt insulation with a proprietary barrier
fitted above to provide a minimum of
50mm for ventilation
Diagram indicating how a
pitched roof with a coved
ceiling below could be
insulated. Note the
permanent ventilation gap
and the insulation around,
rather than under, the
water tank
ventilation zone
Permanent eaves
Where a roof is currently ventilated at eaves level, a
gap of adequate dimension should be left to allow a
continuous 50 mm passageway for air flow. It is
common to find coved ceilings with a collar-tie roof
structure in older buildings. Where this is the case, it is
probably most appropriate to use a rigid form of
insulation for the coved section of the roof, allowing a
50 mm ventilation gap over the insulation for the full
length of the coved area. The horizontal ceiling joists
can then be fitted with any of the insulation products
discussed above.
A habitable roof space can be insulated between the
rafters. Again, it is essential to ensure that there is
continuous ventilation of the roof timbers. In order to
achieve this it may be most appropriate to use a highperformance rigid insulation between the rafters.
As a direct consequence of installing insulation at
ceiling level, the remainder of the roof above the
insulation will be colder. It is therefore important to
insulate water tanks and all pipework to prevent
freezing. Lower loft temperatures also affect older roofs
that have a lime parging between the slates, which
serves to secure the slates and impede wind-blown
rain. In an uninsulated attic, the parging benefits from
the drying effects of the heat coming up from the
building below. Following the installation of insulation,
both the parging and the slates will be colder, leaving
them vulnerable to condensation unless sufficient
ventilation is provided in the roof space.
As part of the complete refurbishment of this
building, the opportunity was taken to insulate the
roof. Rigid insulation has been fitted between the
rafters in the sloping sides with quilted insulation
fitted between the ceiling joists across the top
A roof with largely intact lime mortar parging
applied to the underside of the slates. Parging has
an insulation value in itself and helps to reduce airblown water infiltration
Bats and historic roofs
Bats frequently roost in roof spaces and other parts of buildings. They may be
found under the slates, hanging from roofing felt, parging or timbers and in joints
and splits in roof timbers. Bats do not pose any significant threat to the fabric of a
building nor to the health of its human occupants. Bats are usually only present in
the roof space for part of the year but, as they tend to return to the same roosts
every year, the roosts are protected whether bats are present or not.
Bats and their roosts are protected by Irish and EU legislation. The Wildlife Acts
make it an offence to wilfully damage or destroy the breeding or resting place of a
bat. Even where planning permission has been granted or works to a roof are considered exempted development, the requirements of the Wildlife Acts still apply.
When considering any works to a historic roof, the first step is to have a bat survey
carried out by an appropriately qualified bat expert. Where bats are present or
there is evidence that they have used, or are using a roof, the National Parks and
Wildlife Service of the Department of the Environment, Heritage and Local
Government should be contacted for informed advice and guidance before any
roofing works are programmed and initiated. If there is an active bat roost, works
will need to be programmed to cause the minimal amount of disturbance and
measures put in place to allow bats to continue to use the roof space upon completion.
The most common and effective method of minimising the impact of roof works
on bats is to carry out the work at an appropriate time of the year. The great majority of roosts in buildings are used only seasonally, so there is usually some period
when bats are not present. Maternity sites, which are the ones most often found in
roof spaces, are generally occupied between May and September, depending on
the weather and geographical area, and works should therefore be timed to avoid
the summer months.
Larger roofing projects, however, may need to continue through the summer. The
best solution in such cases is to complete and secure that part of the roof that is
the main roosting area before the bats return to breed. If this is not possible, work
should be sufficiently advanced by May or June for returning bats to be dissuaded
from breeding in that site for that year. In which case, alternative roosts, appropriate to the species, should be provided in a nearby location. Another possible
solution is to divide the roof with a temporary barrier and work on one section at a
time so that the bats always have some undisturbed and secure areas. The advice
of a bat expert should always be sought and there may be a requirement for this
expert to be present on site during the course of the works.
Where it is proposed to treat roof timbers against fungal or insect attack, careful
consideration must be given to ensure that the treatment used will not adversely
affect the bats.
Where roofing membranes are to be included as part of roofing works, they should
be of a type that allows bats to hang from almost any point. Plastic membranes are
mostly unsuitable because bats have difficulty hanging from them, so wind-break
netting stretched beneath the membrane should be used.
The completed roof should be accessible and amenable to the returning bats.
Access to the roof space can be provided in a variety of ways including the use of
purpose-built bat entrances. Bats also need suitable roosting sites and an appropriate temperature regime. This can be provided by the construction of a bat-box
within the roof space that has the advantage also of providing some segregation
between the bats and building’s occupants.
For further information, see the National Parks and Wildlife Service publication Bat
Mitigation Guidelines for Ireland (2006) which can be downloaded from
The improvement of flat roof insulation is more
complex than pitched roof insulation and expert
advice should be sought before carrying out
alterations, in particular to lead roofs. Flat roof
constructions consist of a variety of assemblages of
insulation, structure and ventilation layers. Traditional
flat roofs are likely to be covered in lead or copper
sheet supported on timber boards. It is important to
ventilate the underside of metal-sheeted roofs as, if
condensation is allowed to form on the underside of
lead, it will oxidise, rapidly forming a toxic lead-oxide
powder. If oxidation continues unchecked, holes will
form in the lead, allowing the roof to leak. As internal
access to the structure of flat roofs is often difficult,
they are best upgraded when undertaking repair
works to replace the roof finish above or the ceiling
finish below.
There are a number of points to be remembered when
fitting loft insulation. First, before any insulation works
take place, the roof timbers should be inspected for
fungal or insect attack. Treatment for furniture beetle,
or woodworm, may include coating timbers with an
insecticide, although it is also possible to control
infestation by using adhesive flypaper to catch the
adult borer on the wing. Treatment for fungal
infestation normally involves treatment with a
fungicide. For further information, see Roofs – a guide
to the repair of historic roofs in this Advice Series.
Lead-covered flat roof
Insulation between joists with ceiling
plaster directly below
50mm continuous
ventilation gap below
lead sheeting
A section through a typical traditional flat roof
showing how it might be thermally upgraded.
However, installing insulation at this location would
only be possible if either the roof covering above or
the ceiling below were removed which may not
always be in the best interests of conserving the
architectural qualities of the building
A recently re-covered lead flat roof. These modern
lead roof vents were introduced as, previously, poor
ventilation had caused moisture to build up within
the roof space leading to timber decay
It is important that roof spaces are insulated
thoroughly and consistently. A partially insulated roof
may result in problems with condensation within the
roof space or mould growth on ceilings below
uninsulated areas due to thermal bridging.
Care should be taken with regard to electrical cabling,
particularly older installations within roof spaces. In
general, insulation should be fitted beneath electric
cables to prevent them from overheating which could
create a fire hazard.
The underside of the water tank should never be
insulated as heat rising from the rooms below
provides some heat to the tank, preventing the water
in the tank from freezing. Instead, the exterior of the
tank and the associated pipework should be wrapped
in insulation and overlapped with the remainder of
the ceiling insulation.
All insulating materials placed above the ceiling will
conceal the structural elements from view and also
from inspection. Future access requirements to roof
timbers should therefore be borne in mind when
choosing an insulation product.
In considering how or if the thermal insulation of
traditional walls can be improved, it is important to
fully understand how the existing walls were
constructed, how they were designed to deal with the
Irish climate and the significance of historic finishes to
both the exterior and interior.
an architectural conservation area, generally require
planning permission and may not be considered
Because of the importance of breathability in
traditionally built buildings, any material being applied
to the walls should be vapour-permeable, that is,
should not encourage or allow water or condensation
to accumulate within the fabric of the wall. Walls often
have timbers embedded in them and high levels of
moisture, from whatever source, could create
conditions that promote fungal decay or insect attack
of timbers.
Traditionally built masonry walls in Ireland were
generally constructed of varying combinations of
stone, brick and lime-based mortar, of solid
construction, sometimes with a core of lime mortar
and rubble filling. These materials are porous, allowing
moisture to be absorbed by the wall and later
released, depending on the weather conditions. They
are soft and flexible and can accommodate small
amounts of movement within the fabric. Modifications
to traditional walls should ensure that the
breathability and flexibility of the structure are
As traditional walls are generally of solid masonry,
thermal upgrading can usually only be considered in
two ways: lining the interior of the wall or applying a
new face to the exterior of the wall. Either of these
actions can have a significant effect on both the
character and the physical well-being of a historic
building and, in the context of a protected structure or
Wall finishes are an important element in the quality
and character of traditional buildings and may include
exterior finishes such as cut stone, rubble walls with
dressed openings, brick, or lime render. Internally, there
may be timber panelling, lath-and-plaster or lime
plaster finishes, at times with decorative plasterwork
embellishments such as cornices.
Wall type
Internal finish
Locharbriggs sandstone
Plastered on the hard
550 mm
1.4 W/m²K
Locharbriggs sandstone
Lath and plaster
550 mm
1.1 W/m²K
Locharbriggs sandstone
550 mm
0.9 W/m²K
Plastered on the hard
400 mm
1.1 W/m²K
Craigleith sandstone
Plastered on the hard
600 mm
1.5 W/m²K
Craigleith sandstone
Plastered on the hard
300 mm
2.3 W/m²K
Craigleith sandstone
Lath and plaster
600 mm
1.4 W/m²K
Craigleith sandstone
600 mm
0.9 W/m²K
Kemnay granite
Plastered on the hard
350 mm
1.7 W/m²K
Kemnay granite
Lath and plaster
600 mm
0.8 W/m²K
Kemnay granite
600 mm
0.9 W/m²K
Red sandstone
Plastered on the hard
400 mm
1.3 W/m²K
Blond sandstone
Lath and plaster
600 mm
0.9 W/m²K
Recent research has found that the U-values of traditionally built walls are more favourable than previously
acknowledged. The research identified U-values for differing construction compositions and widths. The results for
walls of varying thickness, with plaster applied directly onto the wall, range from 1.1 – 2.4W/m²K. Correlation was
found between the thickness of the wall and the U-value results (Source: Paul Baker ‘In Situ U-Value Measurements in
Traditional Buildings – preliminary results’)
The wealth of architectural detail and the quality
and craftsmanship of materials used in historic
buildings make them unsuitable candidates for
external insulation. Even where the exterior of a
traditional building is relatively plain, the alteration
of the character and the need to replace window
sills, remodel eaves details and the like would make
the installation of external insulation inappropriate
in many cases
Before considering upgrading, it is important to
ensure that the wall is in good condition, that pointing
is intact or rendering in good order and that obvious
sources of damp such as leaking gutters and rainwater
pipes are repaired. Additionally, the risk of rising damp
can be reduced by ensuring that the external ground
level is not higher than the internal floor level or by
installing a French drain externally to improve the
condition of the wall. In certain cases, injecting a
damp-proof course (DPC) may be considered. While it
is normal practice for modern buildings to incorporate
an impervious damp-proof course to prevent moisture
from the ground rising up through the walls, most
historic buildings were constructed without a DPC.
Installing a DPC in a building which did not originally
contain one can be problematic. Expert analysis of the
problem should be carried out before undertaking any
works of this kind and it is essential to ensure that the
cause of dampness has been correctly diagnosed
before any drastic or invasive works are considered.
For further information see Maintenance – a guide to
the care of older buildings in this Advice Series.
Random rubble stone walls of habitable buildings
would originally have been rendered externally. In
some cases, the original render has been mistakenly
stripped off to reveal the rubble stonework making it
vulnerable to moisture ingress and potentially
reducing its thermal efficiency. The re-rendering of
external rubble walls using a render of an appropriate
specification slows down the loss of heat from the
interior; improves the warmth of the masonry wall;
provides essential protection against the elements
and a barrier to the passage of moisture.
Where there are persistent problems with damp, it is
important to ensure that the external ground level
is lower than the internal floor level and, if
necessary, consider installing a French drain below
ground level with a gravel finish. Water percolates
through the gravel finish to a perforated drain
below, following which it drains to a soakaway at a
distance from the building. The rendered wall finish
will generally require repair following the lowering
of the ground level. The installation of a French
drain around buildings in sites of archaeological
potential, such as churchyards, will require careful
prior assessment and consultation with the relevant
A lime-rendered façade, in good condition, improves
the insulating value of a wall and prevents damp
penetration to the inside of the building
In order to fully exploit the benefits of its thermal
mass, a solid masonry wall would ideally be insulated
on the exterior face. At a basic level, low-density
renders such as lime-based renders achieve this.
Insulation materials which are moisture resistant are
used in combination with special renders to achieve
higher levels of insulation. However, as many external
façades would be completely altered by the addition
of external insulation, it is likely to be inappropriate for
most traditional buildings. Even on buildings with
plain rendered façades, external insulation is
problematic as the thickness of the insulation affects
details at all junctions around windows and sills, eaves
and gutters, doorways and any items fixed to the walls,
at junctions where the building meets the ground and
with neighbouring houses in terraced and semidetached buildings.
External insulation has certain advantages over
internal insulation: the benefits of the high thermal
mass of a solid masonry wall are retained; there is a
reduced risk of condensation between the insulation
layer and the masonry wall; the building fabric remains
dry and heated from the interior and there is no
impact on internal finishes and room sizes. Among the
drawbacks is the fact that the materials are relatively
untried and untested in Irish climatic conditions.
With very careful consideration and specialist
professional advice, there is some potential to upgrade
random rubble stone walls of ruinous buildings or
buildings which have already undergone significant
alterations such as removal of external plaster and
replacement of sills. Intact historic render should not
be removed. Any materials used should be as
breathable as the existing walls. Proposals to insulate
the exterior of a protected structure or a building
within an architectural conservation area will almost
certainly require planning permission. Prior to carrying
out works, it is advisable to consult with the
architectural conservation officer in the local authority.
However, even where a building is not a protected
structure nor located within an architectural
conservation area, planning permission will be
required where the works would materially affect the
external appearance of the structure so as to make the
appearance inconsistent with the character of the
structure or of neighbouring structures.
Mud walling is a relatively fragile method of
construction; being highly susceptible to changes in
humidity, too much drying or wetting can result in
failure of the wall. It is not advisable to undertake
works to insulate such walls either internally or
The upgrading of the interior of existing walls will alter
an internal room to varying degrees depending on the
level of finish. It can be very intrusive and is rarely
appropriate for traditional buildings with interiors of
architectural significance.
Traditionally, walls in Ireland were plastered internally
straight onto the masonry (‘on the hard’). Any addition
of insulation will add to the wall depth, reducing the
size of the room, interfering with the historic finishes
and requiring the relocation of all electrical points and
switches, wall lights and radiators. An increase in wall
depth will adversely affect all decorative finishes such
as plasterwork cornices, architraves, shutters and
skirtings. If the building is a protected structure, such
works are unlikely to be acceptable. Even where the
building does not enjoy legal protection, the loss of
such fine architectural features may not be acceptable
to an owner. A plain room with no cornice and
minimal joinery may be easier to insulate but requires
careful consideration in relation to maintaining the
breathability of the building fabric.
Where they exist, timber stud and lath-and-plaster
lined external walls may provide thermal upgrading
opportunities. This type of wall construction is
relatively unusual in Ireland. Where walls are
constructed in this manner and the lath-and-plaster
has deteriorated and requires replacement, there may
be scope for insulating behind the lath-and-plaster
without increasing the depth of the wall. Intact lathand-plaster should not be disturbed.
As well as the aesthetic and architectural conservation
considerations, there are other potential difficulties in
lining the interior of existing walls. Unlined masonry
walls benefit from interior heat that keeps them dry.
When the walls are lined, moisture ingress from the
exterior and low external temperatures may result in a
problematic build-up of moisture within the original
building fabric. There is also a possibility that
condensation may occur between the insulation and
the wall fabric, resulting in further moisture build up. In
order for moisture in the walls to dry out, any new lining
should be as breathable as the wall itself; even
inappropriate paints can affect the breathability of the
wall. The addition of insulation to the interior also alters
the ability of the building to moderate temperature
through its thermal mass. If an interior is to be thermally
upgraded the insulation should be applied to every
surface, including small areas like window reveals and
the junctions between ceilings and floors above, to
Lining the internal walls of a building will often not
be acceptable, particularly if the walls are finely
decorated as in this Georgian room
avoid any possibility of thermal bridging which could
result in mould growth. This may be hard to achieve,
expensive, and extremely disruptive to the historic
interior and is unlikely to be permitted in a protected
Consideration could be given to insulating parts of
walls such as recessed areas beneath windows where
the wall depth is thinner and therefore likely to be
losing more heat. It should generally be possible to
upgrade these types of areas locally without any
interference with the rest of the room. Window
openings, for example, were often lined with panelled
joinery; the panel below the window could be carefully
removed, fitted with an appropriate depth of insulation
and the panel re-instated. This process is described in
further detail in the following section on upgrading
As interior works to a protected structure or a proposed
protected structure may require planning permission,
the architectural conservation officer in the local
authority should be consulted regarding any proposal
to carry out insulation upgrading works.
Windows, doors and rooflights
Traditional windows are an intrinsic part of the
character of our historic and vernacular buildings. In
Ireland, most surviving traditional windows are timberframed, vertically sliding sash windows with single
glazing. Other traditional windows include casements
or fixed lights of timber or cast iron, leaded lights and
twentieth-century metal framed windows. The quality
of the timber and workmanship found in older
windows is generally far superior to that found in
modern ones and, when properly repaired and
maintained, traditional windows will commonly
outlast modern replacements. For further information,
see Windows: a guide to the repair of historic windows in
this Advice Series.
Between 10-15% of the heat lost from a building can
be through its windows, by a combination of radiant
heat loss through the glass, conductive heat loss
though the glass and frame and ventilation heat loss
through gaps in the window construction. This is low
compared with the estimated average 25% heat loss
through the roof and 35% through external walls. Yet
windows are most often the first target of energy
efficiency works.
In terms of heat retention within a building, older
windows may appear to perform poorly when
compared to some modern windows. It is, however,
possible to repair and upgrade traditional windows to
bring them up to a similar, if not higher, standard than
modern double-glazed windows and to improve the
A pair of houses with well-maintained timber
sliding sash windows
Terraced houses with replacement uPVC-framed
windows. These windows are unsympathetic to the
character of the houses; opening outward instead
of sliding up and down, they disrupt the streetscape;
the modern glass creates jarring reflections; while
the thick frames contrast poorly with the elegant
timber sections of the original sash windows
comfort of occupants without damaging the character
of the building. Prior to considering works, the actual
heat loss through the windows should be considered.
In buildings where windows are small compared to
the overall wall area, upgrading the windows may not
result in a significant improvement in comfort levels or
in energy savings.
When considering the replacement of windows, a
number of factors should be taken into consideration.
First and foremost is the potential effect on the
character of the building and the architectural
heritage value of the existing windows. Also to be
considered are the financial cost, the energy required
to produce a new window, its embodied energy, and
the environmental cost related to disposal of waste.
Modern double-glazed window units are expensive
and high in embodied energy. The initial financial cost
and embodied energy consumption may never be
recouped by cost and energy savings on heating bills
within the serviceable life of such windows. Instead,
simple upgrading of existing historic windows can
eliminate draughts and reduce heat loss. This costs less
and is kinder to the environment than fitting new
replacement windows.
The use of uPVC in traditional buildings should
generally be avoided. uPVC is a material with very high
embodied energy which has a short lifespan as it is
difficult, if not impossible, to repair. Simple wear-andtear often results in whole units requiring replacement
after relatively short periods of time. The manufacture
of uPVC also results in many toxic and environmentally
damaging by-products. In addition, uPVC is generally
not recycled or compressed and must be disposed of
in landfill sites as the burning of uPVC can result in the
emission of toxic fumes.
The installation of uPVC windows in a protected
structure or within an architectural conservation area
is generally not considered acceptable as such
windows would be inconsistent with the character of
historic buildings.
Draughts may result in heat loss and are also
uncomfortable, resulting in a perception that a room is
cooler than it actually is. Draught proofing of a
window will not improve its U-value but stopping
draughts will reduce heat loss and improve the
thermal comfort of the occupants. The overall aim
should be to gain control of the rate of ventilation in
the room concerned.
The first step in reducing draughts is to overhaul the
windows by carrying out any necessary repairs and
ensuring that the sashes or opening lights operate
properly within the frame. A window that is in good
working order can be fitted with draught-proofing
strips. However, with some particular old, delicate or
valuable window frames, cutting grooves to insert
draught proofing will not be appropriate and expert
advice should be sought on alternative methods of
Typically gaps up to 6 mm can be filled with any one
of a variety of available strips including nylon brushes,
pile (dense fibre), polypropylene with foam filler and
silicone rubber tubes. The fitting of strips varies with
A repaired window frame with a replaced style and
new parting bead. The timber sash frames have
been temporarily removed
some fixed to the surface of the frame and others
fitted into the frame by cutting grooves into it. When
fitting a product that requires grooves in the frame
care should be taken to ensure that the joints are not
damaged in cutting the grooves: these are best fitted
by a specialist joiner. Care should also be taken to
ensure that existing ironmongery such as handles,
catches and hinges will continue to function correctly
following draught-stripping and that the colour of the
product is appropriate to the window. Dimensions of
draught strips should be appropriate to the gap to be
filled as larger strips will put pressure on the window
itself and smaller ones will not adequately seal the
gap. Strips should have some flexibility in them to
ensure they will work with the expansion and
contraction of timber between summer and winter
months. Metal and timber casement windows can be
upgraded with similar type draught strips. Casement
windows can also have mastic sealants applied to
form a moulded profile when the opening section is
closed over the mastic to shape the sealant to the gap.
Care should be taken to use a barrier to prevent the
opening window from sticking to the silicone and the
window frame when fitting the seal.
Draught-proofed window frame: brushes are visible
on the staff and parting beads, both of which have
had to be replaced in order to draught proof. For the
brushes to work properly it is important that they
are not painted over
There is a wide range of quality in available draughtproofing products and assurances should be sought as
to the lifespan of a product prior to fitting. In addition,
it is important that the product can be removed easily
without causing damage to the historic window frame
to ensure that when it reaches the end of its life it can
be replaced. It should also be noted that flexible
draught-proofing strips such as brushes and rubber
will cease to operate correctly if painted as part of
redecoration works.
As discussed in the section on ventilation above,
windows in rooms with no alternative means of
ventilation such as wall vents or open flues should
never be fully draught proofed.
External doors in an older building may have become
ill-fitting over the years and so are often poor at
keeping in heat. Traditional doors can be draught
proofed in the same way as windows with various
draught-proofing strips widely available. The bottom
of external doors can also be fitted with a
weatherboard providing this can be achieved without
damage to a historic door. Letterbox brushes or flaps
can be fitted to reduce draughts. For historically
important buildings, discreet draught proofing should
be used. In some buildings it may be possible to
provide a draught lobby to the interior of the external
doors. For a draught lobby to be successful there must
be adequate space to close the external door prior to
opening the internal door. Installing a draught lobby
in a protected structure may require planning
permission and the architectural conservation officer
in the local authority should be consulted when
considering works.
A single sheet of glass will transfer heat quicker than a
double-glazed unit. People feel colder sitting close to
single-glazed windows as they lose heat by radiation to
the cold inner surface of the glass. Tall windows can
result in what is known as ‘cold dumping’, where the
temperature of the air next to window is considerably
colder than the rest of the room, as the cold air is denser
and heavier it falls, or dumps. This is one of the primary
reasons for placing radiators below windows. There are
simple solutions to keeping heat in a room with single
glazing that are more effective than fitting doubleglazed units and more appropriate for use in a historic
building and several of these are discussed below.
Aluminium draught strips can be seen to all sides of
this door. The metal part of these strips,
unfortunately visible, can be painted (although it is
difficult to achieve successfully) but it is important
that the flexible sealant strip is not
Many Georgian and Victorian buildings were originally
constructed with internal timber shutters to the
windows. During the Edwardian period, shutters
began to fall out of fashion and were supplanted by
heavy curtains. The best way to reduce heat loss in the
evenings and at night is to use such shutters. If they
are no longer operational they should be repaired and
put back in working order. Blinds or heavy curtains,
which could include an insulated inter-lining, when
used with the shutters will further improve heat
retention; there are specially designed thermal blinds
available which can improve on this again. There may
be some scope for upgrading shutters using a thermal
lining applied to the rear of the shutter panels; for the
shutters to continue working it is important that the
overall thickness of the shutter is not increased. The
feasibility of upgrading will depend on the available
depth between the shutter panel and shutter frame.
It is likely that the available space will only allow for a
lining depth of approximately 5 to 10 mm. Highperformance, super-insulating linings should be
considered for thin spaces of this type.
Where the original timber window shutters have
previously been removed from a building, or from
parts of a building, consideration should be given to
reinstalling shutters of an appropriate design
accurately based on evidence, for example, from
shutters on an adjoining contemporary building or
from evidence within the building itself.
The window aprons (the area of wall between the
window sill and the floor) can be an area of increased
heat loss as the wall thickness was often reduced at
windows to provide a recessed opening. Where the
window apron is timber panelled, the panels can be
carefully removed and the void behind filled with
insulation. The depth of insulation possible will
depend on the available space between the timber
Working timber shutters: the interior of the shutter
boxes could be lined and sealed to reduce air leakage.
Any new linings should not prevent the shutters from
folding back into the shutter box when not in use
panelling and the external wall. A specialist joiner
should be consulted and appointed to undertake
works to the shutters and window apron.
The shutter box, into which the shutters fold when not
in use, is often a source of draughts that is overlooked.
To reduce or eliminate air movement in and around
the edge of the shutter box, the exterior should be
pointed up with an appropriate material which
remains flexible following hardening and provides a
long-lasting unobtrusive seal between the window
frame and surrounding masonry. From the inside, the
junction of the interior of the shutter box and the wall
should be caulked with environmentally friendly
hemp/lime products or other suitable materials. When
sealing the interior of the shutter box, it is important
to ensure that the caulking does not interfere with the
operation of the sash weights or the shutters, such as
may occur if using expanding foam, which is not easily
A well-sealed shutter lining
For buildings that are primarily used during the day it
may be appropriate to consider secondary glazing.
Secondary glazing is a full-sized window panel fitted
directly inside the existing window, which acts in a
similar way to double glazing. It can be temporary or
permanent and should be fitted to slide or open
inwards in such a way as to allow for easy opening of
the original windows for ventilation purposes,
cleaning and emergency escape. The style and manner
in which the unit opens should be visually appropriate
for the window to which it is being fitted and easy for
the end-user to operate. Any division in the panel
should be located to match the frame of the existing
window, such as at the meeting rail of a sash window.
Duplication of individual panels looks unsightly from
the exterior and should be avoided. Secondary glazing
should be sealed to the interior but the original
windows should be ventilated to the exterior to
prevent condensation forming between the two
windows, which is not only unsightly but is potentially
damaging to the historic building fabric. Therefore, if
secondary glazing is to be fitted, the original windows
should not also be draught proofed.
While secondary glazing is effective it is only
appropriate if it does not affect the character of the
windows and room in which it is fitted. Formal rooms
or rooms with high quality decorative finishes may be
compromised by the fitting of secondary glazing. The
use of the room is also important. If rooms are plain
and used as, for example, offices or kitchens, the fitting
of secondary glazing may be appropriate. If rooms are
not often used during the day it would be more
appropriate to leave the windows as they are and use
any existing shutters.
Secondary glazing should always be fitted in such a
way that it is still possible to use existing shutters.
Slim-line secondary glazing is available which can be
fitted in place of the staff bead between the bottom
sash and the shutters. This allows the shutters and
curtains to be used at night when outside
temperatures are lower. The combination of secondary
glazing, shutters and curtains has the potential to
match the insulation properties of triple-glazed
windows. Secondary glazing alone can result in better
overall thermal performance than a standard doubleglazed window. The fitting of secondary glazing
should be reversible and carried out with minimal
interference to the existing window, shutters and
Inappropriate timber-framed secondary glazing with
frame proportions that do not match those of the
original window, creating a discordant appearance
linings. The fitting of secondary glazing in windows
which retain no historic linings to the interior allows
for more flexibility in the type and size of secondary
glazing frame which may be fitted.
Secondary glazing has the added advantage that it
can be removed and safely stored during warmer
months to maximise solar gain (the heat gained from
the sun through the windows). When sunlight passes
through a pane of glass, its light and heat are
absorbed or reflected; the greater the number of
panes of glass the smaller the amount of heat and
light passing to the interior of the room. It is therefore
advantageous to be able to remove the secondary
glazing during the summer and benefit from the
maximum light and heat from the sun. During the
winter, when the sun is not as hot, the amount of heat
lost from the interior, if not secondary glazed, will
outweigh the amount of heat to be gained from the
sun. Secondary glazing has an additional benefit in
that it reduces the amount of noise which passes
through a window.
An Edwardian window with 1950s secondary
glazing. The secondary glazing is chunky and does
not match the original window profile and blocks
light from the room. The position of the frame within
the opening prevents the shutters from being used
Carefully designed bespoke secondary glazing
installed as part of Changeworks' Energy Heritage
project (Image © Changeworks)
Original or early-replacement windows in a traditional
building should generally not be replaced with
double-glazed windows. Replacing windows in a
protected structure requires planning permission and
this is unlikely to be granted as double glazing will
rarely be in keeping with the character of traditional
buildings; modern double-glazed windows are made
with chunky sections of framing which are necessary
to hold the double-glazed units in place. These
proportions are very different to those of traditional
windows which are generally made of fine timber
The fitting of double-glazed units into existing timber
frames is rarely appropriate or achievable; in order for
the glazing units to be effective at reducing heat-loss
the gap between the glass panes in the unit should be
a minimum of 12 mm, resulting in a total unit depth of
approximately 20 mm including the two pieces of
glass. Historic sash frames are generally finely crafted
from slim sections of timber, the depth and strength of
which would not be adequate to support doubleglazed units. The existing windows would be both
visually and physically compromised as a result. In
addition the aesthetic appearance of the black or
silver edging to the double-glazed units is unsightly.
Double-glazing technology is constantly improving
and research is currently being undertaken to reduce
the depth of double-glazed units, while maintaining
effective U-values. The use of slim-line double-glazed
units may be appropriate in situations where oneover-one pane sash windows require replacement but
not where the existing historic glass survives or where
the new units would be too heavy for the historic
window frames. As with all double-glazed units, the
cost of these high-tech components is unlikely ever to
be recouped over their lifespan, while the gases used
to fill the cavity can have a high embodied energy.
Single glazing
Heavy curtains
Secondary glazing
Secondary glazing
and heavy curtains
Secondary glazing
and shutters
Double glazing
U-value W/m²K
Findings of recent research carried out in Scotland illustrate that existing historic windows with repaired shutters
and appropriate secondary glazing can out-perform double-glazed windows and meet current building regulation
standards (Source: Paul Baker ‘Thermal Performance of Traditional Windows’)
Upgrading traditional rooflights generally involves
some loss of historic character. Older rooflights should
be maintained in good working order. If a rooflight has
reached the end of its working life it may be replaced
with a modern rooflight that matches the existing,
probably timber or steel, with similar profiles. As
rooflights differ from windows in detailing and design,
it will often be possible to incorporate a double-glazed
unit. New, small double-glazed rooflights are available
off the shelf. Light shafts leading to a rooflight should
be insulated in the course of providing roof insulation.
Historic skylights and lanterns, such as this fine
example, should be well-maintained but are rarely
suitable for thermal upgrading
This modern double-glazed skylight allows access
to a concealed valley gutter for maintenance
inspections and cannot be seen from ground level.
It also lets additional natural light into the attic
space below
The ground or lowest floor in a building is the most
important floor to consider for effective thermal
upgrading, unless it is an unheated space, such as a
cellar, in which case the floor above should be
insulated. An estimated 15% of the heat within a
traditional building is lost through its ground floor. In
such buildings, lower floors are of varying construction
types and have different finishes. Both ventilated and
unventilated suspended timber floors are particularly
common at ground floor level. Stone flags, tiles or
brick paving laid on solid floors (often bare earth) are
also common, particularly within basements. In a
public building or church, a range of floor types is
found, often for example, with a stone or tiled finish in
the circulation spaces, typically with an unventilated
timber floor beneath the pews or seating areas.
Improving the thermal performance of the ground
floor reduces the overall heat loss from a building, and
can also significantly improve comfort levels by
providing a warm floor underfoot. In a historically
important building it may, however, be difficult to
upgrade a floor without loss or disturbance of
significant finishes such as tiles or brick paving and
therefore particular care needs to be taken when
considering insulation works to such floors. Planning
permission may be required when lifting such floors to
allow for insertion of insulation. In some cases,
because of the potential for damage to important
finishes, such works may be considered inappropriate.
Suspended timber floors were constructed in the past
both as ventilated floors with vent bricks or grilles in
the exterior walls and as unventilated floors. By the
nineteenth century the latter were less common.
Where vents are provided it is important to ensure that
these remain unobstructed as they ensure that any
moisture which may reach the floor timbers can
escape, preventing a potentially damaging build-up of
moisture levels in the space beneath the floor. If a floor
is not ventilated it may be appropriate to consider
providing vents subject to consideration of the effect
on the visual appearance of the façade. If any vents
have been blocked up in the past, it is important to
reopen them. Vents should not be regarded as the
cause of unwanted draughts as they are an essential
part of the proper functioning of the building and vital
to maintaining it in sound condition. Floor coverings
such as rugs or carpets will eliminate draughts and the
underside of the floor can be upgraded with insulation.
A floor vent to ventilate the ground floor was built
into the wall between the cellar and ground floor
windows as part of the original design
Decorative and high quality floors are difficult to
upgrade and require careful analysis of the time,
cost and, above all, the potential damage that
could be caused to the historic finish in exchange
for improved thermal performance. Fine floor
finishes such as these tiles should not be lifted
If there is a crawl-space beneath the floor it is usually
easier to upgrade suspended timber floors from below
as the joists and floorboards are generally exposed
from the underside. However, if access beneath the
floor is not possible then the floors should be
upgraded from above by lifting the floorboards. Great
care should be taken when lifting old floor boards,
especially the wide boards found in many Georgian
houses; if any are damaged or broken it will be very
difficult to find matching boards for repairs. The fixings
used for old floor boards can themselves be of interest
and can be damaged or lost through careless lifting
methods; strips of metal or timber dowels, were often
used in high quality work to fix boards to each other.
Insulation between floor joists with
mesh below to hold it in place
Vent above ground
Crawl space
Alternatively, floor boards may be tongued-andgrooved together which makes lifting individual
boards difficult to achieve without damage. If working
from below, quilted insulation such as sheep’s wool,
hemp, rockwool or cellulose fibre can be fitted for the
full width and depth of the joists and held in place with
nylon netting stapled to the joists. If working from
above chicken wire or plastic netting can be moulded
around the joists to form trays between them which
are then packed with quilt insulation before the floor
boards are refitted. An alternative method of fixing
from above is to fix battens to the sides of the joists
and fit rigid insulation between them. Note that it can
be difficult to cut the insulation to fit perfectly and any
resulting gaps will compromise its insulating
The easiest way to upgrade an existing solid floor is to
add a layer of insulating material above it with a new
floor finish on top. The covering of an existing floor
should only be considered if it is of no architectural or
historical interest. Floor finishes such as decorative
tiles, brick, wood block or stone flags should not be
covered over although in some cases it may be
possible to carefully lift these to allow for re-laying
over the new, insulated floor. Floors which have
previously been interfered with and have modern
finishes such as concrete are the most appropriate
candidates for covering with insulation. However, this
will increase the height of the finished floor level and
affect internal features such as skirting boards,
window linings, doors and architraves and cause
difficulty at the foot of stairs. Such alterations, in their
own right, can be inappropriate in some interiors and
will need to be considered on a case-by-case basis. The
laying of a new insulated floor over an existing floor
may also reduce the height of the space. Such
modifications to the interior of a protected structure
are likely to require planning permission and the
planning authority should be consulted before any
works are undertaken.
A typical detail for upgrading
a ventilated suspended timber
floor. The insulation is held in
place with nylon netting
(indicated by the dotted line)
fixed to the underside of the
floor joists
Basement floors are usually solid. The use of the
basement should be considered prior to upgrading
the floor and if it is used for activities not requiring
heat it may be appropriate to insulate above the
basement level instead. Expectations for a warm,
insulated, dry basement may not always be realisable
in older buildings.
If a building is undergoing restoration or major
refurbishment, the opportunity may be taken to lift or
excavate the existing floor and to lay insulation on a
new subfloor. However, this option should be carefully
considered for a number of reasons. The excavation of
an existing floor and the laying of a new floor slab can
in some cases undermine walls which have very
shallow, or indeed sometimes no, foundations or
footings. Vibrations arising from the works can also
potentially cause structural damage. Care should be
taken in buildings built over a high water table or with
pre-existing problems with rising damp. It is possible
that, as a new sub-floor will seal the floor, moisture
which previously evaporated through the floor joints
will now be trapped and may be forced to make its
way over to the walls, thus increasing the risk of
damage to fabric from rising damp. If it is decided to
lift a floor for the purposes of adding insulation, it may
be worth considering the installation of underfloor
heating as part of this process. Underfloor heating is
most effective when laid in solid floors with a hard
floor finish such as stone or tiles. Traditional buildings
may benefit from the low levels of consistent heating
provided by underfloor heating at ground level as it
will help keep the bottom of walls dry.
There is considerable interest in the use of vapourpermeable flooring construction, using concretes
made of lime with hemp or expanded clay. These
materials may be appropriate where there is a delicate
moisture equilibrium to be maintained. Circumstances
which require a radon barrier would make the case for
using such materials less compelling. Building
Regulations also imply that new floors should be
The properties of historic buildings (high thermal mass
and slower response time), together with issues related
to the installation of services mean that systems which
are not usually considered for use in modern buildings
can be most appropriate in historic buildings.
Solutions are not always as simple as they may seem
and a holistic approach should be taken to looking at
the benefits as well as the future consequences of any
given system. Also, technology in this area is
constantly evolving and new products are regularly
becoming available. The efficiencies of differing
heating systems that are used in Ireland can be found
on SEAI’s Home-heating Appliance Register of
Performance (HARP) database.
Solid stone floor: upgrading a stone-flagged floor
such as this would inevitably result in an
unacceptable level of damage or breakage of
individual flagstones and should be avoided
As the opportunities to increase insulation in a
traditional building are relatively limited, building
services and their controls can play a large part in
improving energy efficiency. In most traditional
buildings, building services such as heating systems,
plumbing and electrical installations are not original
to the building and there may therefore be some
flexibility in altering them.
Heating systems, plumbing systems and electrical
installations normally have a shorter life than their
host building; electrical installations are typically
renewed every twenty-five years, piped services less
frequently. There is scope when renewing such
installations to significantly improve the energy
efficiency of a traditional building, always bearing in
mind that intrusive works to protected structures
require careful consideration and should only take
place after professional conservation consultation,
advice and detailed design which take fully into
account the value of the existing fabric.
Many historic buildings, particularly those in isolated
rural locations, had systems for collecting and storing
rainwater. Where old collection systems survive, such
as lead or copper tanks in the upper reaches of
buildings, water butts or water barrels, it may be
possible to bring them back into use as a water
conservation measure and for use in activities such as
watering the garden or washing cars. Overflow
systems, safety systems and protection against
flooding should be put in place and maintained.
Any proposal to use collected grey water (waste water
from such domestic activities as clothes-washing, dishwashing and bathing) for use within the building or for
use in appliances should be based on expert advice.
Water supply and drainage services increase the risk of
damage when used on upper floors, plaster ceilings
being most at risk. The greatest risk is from a burst
pipe in the roof space, usually caused by an
uninsulated pipe freezing during the winter months.
To prevent this, all water services pipes outside of the
insulated envelope of a building should be lagged.
As discussed elsewhere in this booklet, designers of
older buildings were sometimes surprisingly
sophisticated in understanding buildings, their
ventilation and heating. While innovations in services
tended to be applied to institutional buildings,
elsewhere there is evidence of successful
technologies, such as the use of cast-iron radiators.
Heavy cast-iron radiators, emblematic of nineteenthcentury applied technology, were an important
invention, durable and efficient. Their moderately slow
response time is particularly suited to avoiding
thermal shock, that is, an abrupt change in
temperature, in older buildings. Churches, in particular,
often retain components of nineteenth-century
heating systems, where large pipes carrying hot water
were laid in trenches covered with open cast-iron
grilles, or arranged at low level around walls or
between pews. These systems work on the principle
that hot water rises, so that a boiler was located at
basement level and the hot water circulated under its
own thermodynamic impulse through the pipes,
heating the spaces it passed through.
Existing holes in floors or notches in joists can be
reused to accommodate new runs of services.
New holes or notches should not be created to
avoid further weakening of the joists which has
occurred in this example. Where there is existing
pugging within the floor space, it should
preferably be left in place
Hot-water heating pipes in a typical nineteenthcentury floor duct
Ferrous metals in contact with water are prone to rust
and so such systems have tended to deteriorate.
Historic cast-iron radiators may sometimes be in
sufficiently good condition to warrant reuse. However,
a careful evaluation of the risk of leaking or flooding
should be made. While modern hot-water-based
central heating systems employ pumps and contain a
comparatively small amount of water, there is no
technical reason not to employ sound old radiators,
and indeed the advantage of the thermal mass of the
cast iron and the moderate heating up and cooling
down time associated with them means that they are
good to use in historic properties.
When pipework was retrofitted into buildings, the
pipes were often ill-fitting, leaving gaps for draughts.
Equally, when such pipes were removed in the past,
the resultant holes were not always fully closed up.
These holes may admit water, air or even smoke in the
event of a fire and should be properly sealed up.
Older buildings were originally heated with open fires
but it is likely that this form of heating is now
superseded in many houses. Open fires are very
inefficient with only 30% of the heat being emitted
into the room. In most buildings open fires will be
New and redundant holes in floors should be made
good, fire-sealed where appropriate, and finished to
match the existing floor. Where new service runs
would interfere with the fabric of a protected
structure, planning permission may be required
supplemented or have been replaced by a central
heating system fuelled by oil, gas or timber fired
boilers. While boilers are more efficient than open fires,
typically operating at approximately 70% efficiency,
significant improvements in efficiency have been
made in recent years with 95% efficiency boilers now
available. This means that 95% of the energy in the
fuel is converted to heat resulting in less fuel being
burned for the same heat output. The upgrading of
standard boiler systems and associated controls in
traditional buildings can be a relatively
straightforward process with little negative impact on
historic fabric. Condensing boilers are much more
efficient and smaller than older ones and, when
combined with appropriate controls, have the
potential to deliver significant increases in energy
efficiency. Wood pellet boilers are also a low carbon
replacement for existing boilers. Care should be taken
regarding the location of any new boiler as the flue
vents may have a negative impact on the external
appearance of the building and may not be
considered acceptable. To benefit fully from a high
efficiency boiler, the heating controls in a building
should also be upgraded to include thermostatic
radiator valves (TRVs), room thermostats, heating
zones, water heating on a separate time and
temperature control, a programmable timer, boiler
interlock and load compensators or weather
compensators. If a building is fitted with a high
efficiency boiler it is more efficient to run summertime
water heating off the boiler rather than an electric
immersion heater provided that the hot water circuit
can be separated from the heating circuit. The lagging
of all pipes carrying hot water is also cost effective, but
may be difficult to implement in an existing building
where many pipe runs are located below floors or
within ceiling spaces.
Many traditional buildings have chimney flues that
could be used to advantage with wood burning
stoves. A stand-alone stove as a replacement for an
open fire would not normally have a boiler but there
are a limited number of small stand-alone room stoves
available with integrated boilers that can be
connected to radiators and a hot water system. Stoves
can be up to 80% efficient as opposed to the 30%
efficiency of an open fire and can be used to burn logs
that are sourced locally. The burning of timber is
considered to be carbon neutral as trees absorb
carbon dioxide while growing. However, in the case of
pre-dried timbers or wood pellets, the timber may no
longer be carbon neutral. Consideration should be
given to the embodied energy already contained in
wood if purchasing kiln-dried timbers or if using
processed wood pellets imported from a distance
(wood pellets are commonly imported from central
Europe). Larger wood-burning boilers are also
available and these are usually located remotely from
the building in an outhouse with a wood storage area
and a hopper for automatically feeding the boiler.
Fuel storage requirements for pellets and logs can be
substantial and the construction of a new storage
structure within the curtilage of a protected structure
or in an architectural conservation area may require
planning permission.
Wood-burning stoves can be efficient but in a
traditional building they should generally only be
fitted into non-decorative fireplaces. Historic grates
and fire surrounds should not be damaged or
removed in order to fit a stove
The use of electricity as a source of energy for heating
is generally inefficient due to losses in generation, in
distribution and in the appliance itself, with high
resultant carbon dioxide emissions per unit of heating
output when compared to oil or gas heating systems.
The use of electric heating will also have a negative
impact on a building’s Building Energy Rating, as it is
deemed to be inefficient and carbon-intensive: this
may change in the future with increased use of wind
and hydro-power. However, in the context of a historic
building or a protected structure, the installation of
wiring for an electrical heating system may be much
less intrusive than a piped water-heating system, with
no risk of damage to the fabric of the building from
water leaks. Storage heaters are relatively cheap to
purchase and can use night-rate electricity effectively
(the use of which has some positive environmental
implications). They can also exploit the high thermal
mass of an existing building and, when coupled with
appropriate draught-reduction and insulation and
modern control systems, can prove to be an optimum
solution for heating a historic property. Similarly the
use of panel heaters with a shorter response time,
perhaps used in tandem with storage heaters, or
convector heaters/coolers could be considered. The
location of cable runs either above or below floors
(surface-mounted or otherwise) will need careful
consideration to ensure minimal damage to fabric, in
terms of both visual and physical impacts.
However, in the medium term, market forces are
expected to drive down the costs of installing
renewable energy technologies, shortening the
payback periods, thus making the installations more
cost effective.
In the context of relatively high demand for energy
within a particular building, the payback time on
space-heating equipment which uses renewable
energy, such as biomass or heat pumps, will be shorter.
They should also assist in cutting carbon emissions.
A storage heater fitted in a Georgian house. The low
height of the storage heater allows for operation of
the shutters at night and does not block the window
Most heat recovery systems for domestic situations
rely on a managed ventilation system, based on
electrically powered fans, in the context of tightly
sealed new buildings. As discussed previously, there is
concern that significantly reducing ventilation within a
traditionally built building may cause moisture
problems within the fabric and in rooms. It seems
unlikely that a heat recovery system in a
predominantly naturally ventilated building would be
either cost- or energy-efficient. In addition, any
mechanical system that relies on ductwork will
probably encounter difficulty as the relatively large
ductwork would inevitably entail unacceptable levels
of disturbance or loss of historic fabric or give rise to
visual impacts. In the case of a protected structure,
such works would probably require planning
Upgrading the fabric and services of an existing
building are usually the most cost-effective means of
improving its energy efficiency. However, there are
instances where, to achieve greater energy savings
and reduce carbon dioxide emissions, the use of
renewable energy technologies could be considered
for small-scale generation of electricity. So-called
‘micro-renewables’ include small-scale devices for
exploiting sun and wind power, and heat within the
ground, as well equipment for using renewable fuels
such as timber, biomass or wood pellets. At present,
the economic case for installing micro-renewables is
not strong in terms of payback through cost savings.
High capital costs result in lengthy payback periods
which often exceed the lifespan of the installations.
Using simple solar-powered water heaters for
domestic hot water is probably the most effective way
to actively exploit solar power. Solar panels when
mounted on the roof of a traditional building can be
visually intrusive; a roof slope with a southerly
orientation, not visible in important views of the
building, is ideal such as within the valley of a roof.
Such an installation can be reversed without causing
significant damage, and so may be suitable for use on
protected structures and within architectural
conservation areas, subject to planning permission. It
should be remembered that solar panels require an
enlarged water cylinder.
A roof valley may be an appropriate place to locate
solar thermal or photovoltaic panels provided that
the orientation of the roof is appropriate. This
image shows solar panels installed in hidden roof
valley as part of Changeworks' Renewable Heritage
project (Image © Changeworks)
The installation cost of a typical photovoltaic array for
a dwelling is still relatively high. Small-scale windturbines are unlikely to offer any benefit in an urban
environment although well-located installations, with
a good exposure to wind, may be worthwhile in a rural
situation. Power from such an installation could be
used for water heating or background space heating.
Wind turbines generate a large amount of vibration in
use and are subject to high wind loadings and these
must be taken into account if considering attaching
one to an older, possibly fragile, building. Also, the
visual impact of a wind turbine on a historic building
may be unacceptable. It is recommended that the
building be checked for structural stability by an
appropriately qualified professional before a wind
turbine is attached.
Small-scale combined heat and power plant (CHP) can
be very efficient in institutional or commercial
buildings with high and consistent heat demands such
as hospitals, nursing homes or hotels.
The installation of micro-renewables on a protected
structure is not considered exempted development if
it would have a material effect on the character of the
building. The architectural conservation officer in the
local authority should be consulted when considering
any works.
Heat pumps work on the same principle as a
refrigerator, drawing heat from a source, sometimes
the air or ground water or the soil, and putting it into
water or, less commonly, air. Such heat pumps work
best serving as a source of heat for underfloor heating,
where the water temperature required is lower than
for radiators. Normally they are driven by electricity
and are often claimed by their manufacturers to have
the ability to convert one unit of power into three
units of heat, thereby making the use of electricity for
space heating more economic. If properly designed
and installed, heat pumps may represent a carbonefficient form of space heating. Systems should be
designed for appropriate applications for all weather
Air-to-water heat exchangers: a heating system
provided to a converted stable building. The grey
metal casing will be camouflaged by future
As heat pumps are usually only appropriate for use
with underfloor heating the retrofitting of this type of
system is difficult. This type of upgrading should
usually only be considered in the context of largescale refurbishment works. Where the installation
would involve loss of historic fabric it may not be
suitable in a protected structure and planning
permission would most likely be required. It is also
worth noting that the appearance of air source heat
pumps, which are large and industrial-looking, may
not be appropriate sited adjacent to a traditional
building and their location will therefore require some
careful consideration.
Many traditional buildings were designed for
optimum use of daylight; effective use of daylighting
can reduce the need for artificial lighting. Careful
design of switching arrangements and other controls
for lighting such as occupancy detectors are effective
ways of reducing energy use in buildings.
The most efficient sources of artificial light are
fluorescent tubes (which use 80% less energy than
traditional incandescent bulbs) and light emitting
diodes (LEDs). As compact fluorescent lamps (CFLs)
emit higher levels of ultra-violet light which leads
fabrics and papers to fade, consideration should be
given to the potential impact on a room’s decorative
finishes and furnishings prior to switching from
traditional incandescent bulbs. Recently developed
halogen lights use less energy than incandescent
bulbs but do not cause the same problems with
fading as CFLs. According to the marketing
information these halogen lights use 30% less energy
than traditional incandescent but have a similar
appearance and may be more appropriate in formal
rooms and older types of light fittings. In this regard, it
should be noted that some light fixtures in protected
structures may be important features in themselves
and modification of them may require planning
Principles for improving the energy efficiency
of a traditional building
> Consider the microclimate and respond as appropriate: take advantage of the
sun, create protection from the wind and keep buildings well-maintained and dry
> Ensure the nature of use is suitable for the building as a whole or for particular
rooms within a building. In some cases, it may be appropriate to re-arrange the
locations of activities within a building
> Evaluate the energy requirement in the context of embodied energy and life
cycle costs as discussed in Chapter 1
> Understand why and where heat is lost. Recognise energy-efficient design
features in traditional buildings and endeavour to retain and improve these
> The principle of minimal intervention should apply when undertaking works
to upgrade the energy efficiency of a historic building. Retain and repair the
existing fabric of the building rather than replace it
> Prioritise the order in which building elements are to be upgraded, taking into
consideration both the character of the historic fabric and the upgrading
works which will provide the greatest energy savings when compared to the
investment costs. In general, for a traditional building, the priority order will
be as follows:
Draught proofing of windows and doors
Roof insulation
Replacement of outdated services with high efficiency units and updated
Repair of shutters and fitting of curtains, with the possible installation of
secondary glazing
Floor insulation
Wall insulation
> Follow the principles of passive design when making any modifications.
If constructing an extension to an existing building, take full advantage of
passive design using this new addition to incorporate elements such
as micro-renewables, which can serve both the new and old parts of the
building. However, bear in mind that it may not always be appropriate or
practical to add to the older building
4. Case Studies
These case studies demonstrate how measures to
improve energy efficiency have been implemented in
a variety of historic buildings without negatively
impacting on the architectural character of each
building. In addition they show how, by following the
conservation principle of minimal intervention, a
sustainable level of intervention can be achieved in
terms of the cost of works and the amount of energy
to be consumed by a building over its prolonged life.
return level of the original stairs and later removed.
The building, like so many in the inner suburbs, was
converted to flats in the 1960s and extended at that
time with a flat-roofed extension to the rear. Following
re-conversion to a single dwelling in the late-1980s,
the roof was raised to provide a further habitable floor.
The building extends to approximately 220 m².
This is an example of a house which has been adapted
many times to meet changing requirements. It is now a
protected structure and any works that would materially
affect its character require planning permission.
A Regency house in the city
Recently constructed elements such as the attic storey
were built to the requirements of the building
regulations. This means that the roof and much of the
back wall have higher U-values than the original
structural elements. Works to the house included
replacement of the basement floor in concrete, with
insulation beneath the slab. The roof has a typical
modern slated construction, with a high performance
insulation board laid between the rafters, laid over foilbacked plasterboard. The flat roofs are covered in
asphalt and insulated with a fibreglass quilt. The original
brick wall above basement level, which is the main
façade, was repointed in sand and cement in the 1960s.
This has interfered with the ability of the wall to
‘breathe’, that is, to allow water to evaporate, and thus
the wall is colder than a comparable wall pointed in a
lime-based mortar.
The brick façade from 1821 was later repointed using a
sand and cement mortar. While the removal of this
pointing and its replacement with a vapour-permeable
lime-based mortar would benefit the building, it is
likely that the process of removal of the pointing would
cause unacceptable damage to the brickwork
The house faces south-west, and is in the middle of a
terrace of similar houses. This early-nineteenth-century
house has been modified many times over its lifetime.
The original layout comprised two rooms on each of
the lower two levels with a three-bedroom layout on
the upper floor. A ‘flying bathroom’ was added on the
In common with many such buildings, the basement
walls are thicker and are constructed of granite in a
lime mortar. The granite, being dense, is a colder
material than the brick and conducts heat more
rapidly. New windows are double glazed in a timber
frame, while original windows, where existing, are
single glazed with working shutters. No draught
proofing has been applied to the windows.
A gas boiler provides heat to radiators and a hot water
cylinder. In addition, an open fire is lit in the main
living room and a solid fuel stove is used in the
basement family room.
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This hybrid construction, combining historic and
modern fabric, is relatively common, particularly as
many older houses have been renovated or extended
in recent years. Conservation considerations have
meant that the main windows have been retained and
that no dry-lining has been applied to the walls of the
house while surviving original fabric has been retained
Temperature Profile Line 1
This thermographic image of the front wall
indicates the temperature of the different parts of
the façade, red being the warmest and blue the
coldest, with yellow and green as intermediate
temperatures. High temperatures indicate where
most heat is being lost from the inside of the
building. On the image it can be seen that the
windows are losing the most heat, and how the
areas of the wall which are known to be damp are
also losing heat at the same rate as the single
glazed windows. Equally it is possible to identify an
area where a small portion of walling was
reconstructed using sand and cement mortar
Being in a terrace, the house benefits from the lack of
exposure of its flanking walls. The configuration of the
house, being approximately a cube, means that heat
loss through the walls is low and the heat loss through
the roof and basement floor is comparatively low
given high standards of insulation and a relatively
small ‘footprint’ of the building relative to its overall
floor space. The orientation of the house means that it
enjoys some solar gain through its front windows and
it is sheltered from the prevailing winds by mature
trees located about twenty-five metres away. The
building has a typical family-based level of activity,
with continuous light daytime occupation and more
intense morning, evening and night-time usage.
Shutters are used to reduce heat loss through the
historic single glazing at night-time, while there are
lined curtains on some windows.
The cumulative effects of the various works that have
been undertaken in recent years mean that it is in
good condition with a re-slated roof and new back
wall. These elements of the house should not require
further works for another 50-70 years. Windows and
cast-iron rainwater goods will require on-going
maintenance every 5 years.
Some draught proofing could be added to the existing
historic sash windows. Gaps between the window
frame and the wall should be caulked to minimise
leakage. Dampers could be provided to all chimneys to
moderate ventilation rates. For architectural
conservation reasons, there is little potential for the
provision of porches or draught lobbies either
internally or externally. The removal of the cement
pointing and its replacement with a vapourpermeable, lime-based mortar would improve the
thermal performance of the front wall by reducing its
moisture content. However, the potential for damage
to the brickwork, and the relatively high cost of such
work make repointing undesirable from a
conservation point of view and financially unviable.
When the present gas-fired boiler reaches the end of
its life, a new high-efficiency condensing boiler with
new heating controls could be provided. The hot water
cylinder should be on separate time and temperature
control. Pipework should be insulated where
accessible. All incandescent light bulbs should be
replaced with low energy bulbs.
A detached country house
When compared to buildings in other northern European countries, Irish buildings generally have comparatively
small windows in proportion to the walls
This is a fine two-storey over basement country house,
primarily dating from the early-eighteenth century but
with nineteenth-century additions. The building is a
protected structure and is in use as a private dwelling.
The floor area of the house is approximately 300 m².
The layout of the house is quite compact, having a
central entrance hall, with rooms to either side, leading
to a stair hall, which originally projected from the rear
wall, but was later partly flanked by the nineteenthcentury extension to the rear left. The house retained
much of its original joinery and plasterwork but was in
need of repair. Walls are constructed in rubble stone
and rendered externally.
The siting of the house demonstrates a good
understanding of the benefits of shelter-belt planting,
having a large copse extending to the west with farm
buildings and more trees extending to the east. The
façade of the house itself faces due south.
A programme of repair works has been ongoing at the
house for a number of years, benefitting from grant
assistance from the local authority conservation grant
scheme, the Heritage Council and the Irish Georgian
This first edition Ordnance Survey map shows a
more extensive stand of trees to the northeast, with
several clumps of trees ornamenting the front
paddock and modifying the impact of the
occasional mild southerly gale
Generally, essential repairs to the external envelope of
the building have been carried out on a sequential
basis. Typically a dry house is a warmer house and with
that in mind, the roofs were re-slated, parapet gutters
re-leaded, chimneys re-rendered and defective
rainwater goods repaired or replaced - all with a view
to reducing the level of dampness in the house.
Ceilings under the attic have been insulated. Original
window frames have been repaired and, where sash
windows had been replaced with inappropriate
twentieth-century ones, these were replaced with
sashes to match the original. No draught proofing has
been installed as the newly fitted sashes are quite
snug, while still admitting sufficient trickle ventilation.
Works which have been carried out for the benefit of
the structural integrity of the building have also
increased the building’s thermal performance. No
insulation has been added to the walls of the building
but, by keeping them dry, the building stays warmer
and retains heat better. The omission of draught
proofing from the windows means that they admit
more ventilation, which helps to dispel high internal
moisture levels which could cause or promote the
growth of mildew, rots or other fungi.
An oil-fired aga cooker was fitted in the new southfacing kitchen/dining room. The nineteenth-century
wing is heated by an oil-fired central heating system.
An electric hot-water immersion cylinder is also used.
This house represents the implementation of a series
of measures which can significantly improve the
energy efficiency of a traditional building. The
combination of attic insulation and new or repaired
windows together with its south-facing orientation
have helped significantly to exploit the thermal mass
of the building in retaining solar heat-gain. Virtually all
rooms have fireplaces, which have been kept open.
The relocation of the main kitchen from the northfacing rear room to a sunny east and south-facing
room made a significant improvement to the daily
comfort of the occupants.
More than 260 years old, the original finishes still
survive internally. The newly re-slated roof has a
design life of a hundred years. The new timber sash
windows, with normal maintenance, have a life
expectancy in excess of 100 years.
The house should be re-rendered with a lime based
render, which would further reduce the moisture
content of the walls, keeping them warmer. In a rural
location with sufficient space for storage of fuel, a
wood-pellet boiler may be considered, or a more
labour-intensive wood-burning boiler, which could
exploit timber harvested on the farm. In the lessarchitecturally important rooms, provision of small
timber burning stoves could be considered; these
would do away with the need for central heating
pipework, with the potential for damage to the fabric
of the building. For those areas served by the central
heating system, the different zones and the supply of
hot water should be time and temperature controlled
from a central programmer. There should also be a
boiler interlock and, for a large house, a compensator
circuit. The installation of an optimiser control that
senses outside temperature should be considered. All
hot-water pipework should also be insulated.
Temporary sealing through the use of dampers on
unused chimneys would reduce infiltration losses.
Where appropriate, traditional light bulbs should be
replaced with energy-efficient ones.
A pair of rural cottages
New gas-fired condensing boilers have been provided
and serve underfloor heating and radiators. Each
house has three heating zones with separate
thermostats. All radiators have been fitted with
thermostatic radiator valves. Wood-burning stoves
have been fitted in the living room fireplaces and
these chimneys are therefore still in use.
Cottages prior to refurbishment
These small lodges, which are protected structures, had
fallen into disrepair before undergoing refurbishment
and enlargement. Small simple buildings such as these
are most vulnerable to over-renovation, where their
character can be lost.
Poorly built modern extensions to the cottages were
replaced with modern, highly insulated extensions
with window openings primarily facing east and west.
Sun rooms were added on the south side of the
houses, providing pleasant living spaces and
contributing to the solar gain of the buildings in their
entirety. As the cottages are semi-detached, the new
extensions to north and south leave only one exposed
original wall in each cottage. The ground floor was
excavated and a new, insulated floor laid while the
roof was insulated as part of the re-slating works.
Historic leaded single-glazed windows have been
retained and repaired. As a result of the repairs these
windows have a snug fit and have not required
draught proofing. Where existing, original shutters
were brought back into use. New timber doubleglazed windows, some with shutters, have been
provided elsewhere. External render was replaced in a
lime-based render which matches the original. A
French drain was provided around the building to
help reduce the moisture content at the base of the
external walls.
These houses have modern standards of insulation in
the floor and roofs. While the walls have not been
upgraded, the new extension to the north side of the
building has modern insulation standards thereby
keeping the coldest part of the buildings warm. The
sun rooms to the south will collect heat from the sun
and this heat will gradually spread through the house
during the day. As the sun rooms are separated from
the rest of the house with external-quality doubleglazed doors they can be isolated in the evening and
during the winter. The radiators in the sun rooms, on a
separate circuit to the remainder of the house, can be
controlled independently. The shutters keep in the
heat at night time.
The cottages have been upgraded in a manner which
achieves a balance between improving energy efficiency
whilst retaining the essential character of the historic
lodges as well as their building elements and materials.
The new roofs, using high quality natural slate and
leadwork, should have a design life of 70-100 years
subject to regular maintenance of the rainwater goods.
Having upgraded the cottages and introduced a range
of energy-efficient measures, the buildings should be
kept in good repair and maintained in an appropriate
A converted stable yard
Before and after images of restored stable yard
This is a stone-built stable yard arranged around four
sides of a courtyard. The stable yard is a protected
structure and, prior to refurbishment, it had fallen into
an almost completely ruinous state. The footprint of the
building is extensive and the ranges are long and low
with a shallow plan from front to back. The building is
set low in relatively open landscape but with a copse of
trees planted on its west side.
Each house is served by an air-to-water heat pump,
which provides heat for underfloor heating at ground
and first floor levels through the houses, as well as
domestic hot water. Every room in each house is
thermostatically controlled. Each heating system
benefits from a weather compensator, which modifies
the output in accordance with the external air
The complex has been subdivided into a group of ten
houses. As part of the restoration of the courtyard, the
building was re-roofed, with high levels of insulation
provided. New windows were installed in both single
and double-glazed arrangements. Where existing
windows survived, these were repaired and fitted with
single glazing. The design of all the new windows was
based on evidence of pre-existing four-pane windows.
These new windows are double-glazed casement
windows. The solid rubble limestone walls were
repointed with a lime mortar in order to ensure high
levels of breathability while a new insulated floor slab
was laid with an injected DPC being provided at low
level to the original walls. New, well-insulated
extensions complying with the building regulations
were provided to four of the houses. This has
internalised part of the north wall of the complex,
making that wall warm and dry.
Refurbishment of an existing ruin is sustainable
development in that it retains embodied energy by the
reuse of a structure which has already had a 200-year
life. The new floors and roofs have been insulated to
modern standards and many rooms within the
complex have double-glazed windows. The heating
system is designed for optimum efficiency.
Having fallen into dereliction over a period of several
decades, this building has now been comprehensively
restored and refurbished and is being put to a new and
sustainable use. The essential character of the stonewalled, slate-roofed structure has been maintained
with modifications to its architectural form being kept
to a minimum while at the same time ensuring suitable
comfort standards.
The building complex has been restored to high
conservation standards with natural slate roofs, new
floor substrates and new floors all of which have an
anticipated 100-year life. The windows and cast-iron
rain-water goods will require regular maintenance.
The air-to-water heat pumps have a life-expectancy of
15 years.
This detached building is two-storeys in height over a
basement and has an additional attic storey set behind
a parapet. The corner stone was laid in 1703 and the
building completed by 1707. However, it is believed to
incorporate fabric from a seventeenth-century building
that previously occupied the site. The seven-bay brick
façade is asymmetrical with a corresponding
asymmetrical plan. Accommodation to the west side
includes a basement, double-height hall and attic,
while the east side has accommodation over the
basement, ground, first and attic levels. The staircase is
contained in a projecting compartment at the rear of
the building. A single-storey extension was built c.1995
on the north side of the hall to the east of the staircase
Having upgraded the courtyard buildings and
introduced a range of energy-efficient measures, the
building should be kept in good repair and maintained
in an appropriate fashion. As the use of air-to-water
heat pumps is relatively new to Ireland, it would be
interesting to monitor the performance of the system
over a number of years and calculate the energy
savings achieved.
A mixed-use building in a town
This building is a protected structure. It comprises a
series of large rooms that are used for private functions
with ancillary kitchen and WC accommodation. Office
accommodation is located in the smaller rooms within
the attic storey and first floor of the building. The
building is approximately 300 m² in area.
The interiors have changed considerably during the
course of the last three hundred years. In particular,
dereliction during the middle period of the twentieth
century resulted in considerable loss of architectural
features. Today the most important surviving feature is
the original timber staircase. The ground, first and
second floors are of timber joisted construction with
floorboards supported by beams or load-bearing walls.
The basement floor consists of modern tiles on what is
understood to be an uninsulated 1970s concrete slab.
The walls of the basement are of calp, a dense
limestone, which has been stripped of its internal
plaster, while the walls of the upper storeys are of brick,
exposed externally and plastered internally.
The existing pitched roof is finished with natural slate.
The interior of the roof space was originally built to
accommodate habitable space with dormer windows
provided in the roof. These rooms are in use as offices
today, retaining dormer windows with dry lining to the
walls and the underside of the roof. The roof-space
contains some fibreglass insulation. The existing
windows and doors date from the 1970s and are
replicas of the historic sash windows.
Tall, south-facing windows allow the main hall to be
flooded with light and maximise solar gain
Having undergone a significant restoration in the
1970s, the building has been the subject of periodic
maintenance and repairs since that date. Recently,
repairs and draught-proofing works have been carried
out to the windows and there has been some
upgrading of services.
Built in 1703-7, the building is now more than three
hundred years old. The brickwork, being mainly original,
has discounted its embodied energy over its long
lifespan. The slating has been repaired a number of
times, but is nearing the end of its useful life.
The building has recently been fitted with an efficient
gas condensing boiler resulting in immediate savings
in terms of energy consumption. However, the
distribution pipework is old and in need of upgrading.
Hot water is provided locally from under-sink electrical
units; this can be an efficient solution where water
demand is sporadic. Prior to carrying out full-scale
replacement of the existing pipes, an assessment of
any potential damage to the fabric should be
completed and if it is found that this work would result
in further damage to the fabric it may be more
appropriate to modify the existing pipework without
general replacement.
This is a free-standing building with relatively thin
walls and extensive single-paned glazing. While it
benefits from a southerly orientation the building has
a high heating requirement. The building enjoys good
natural daylight from the south with large window
openings and fewer openings on the north elevation.
There are fireplaces at basement and main floor level
in the north wall, while the staircase is also on the
north side. The single-glazed southerly windows are
advantageous as they allow for maximum amounts of
solar gain. The windows and doors, prior to draught
proofing, provided ventilation levels above the
required 0.8 - 1 air change per hour. This was especially
noticeable in the smaller office spaces at the top of the
building, which were difficult to heat, and had a
negative impact on comfort levels.
While the building was substantially renovated in the
1970s, it retains much of its original fabric and spatial
character. The recent upgrading works to the building
have been achieved with the maximum retention of
historic fabric and no noticeable impact on the
character of the building.
As the basement floor is modern, there is the potential
to replace it with an insulated slab incorporating
underfloor heating powered either by natural gas or
connected to a source of renewable energy. However,
digging up the basement floor would be a costly
exercise, which would only make financial and
environmental sense if undertaken as part of a larger
project to refurbish the basement and enhance the
architecture, thereby going some way to mitigate the
cost both financially and in relation to embodied
energy. Given the location of this building, and the fact
that it incorporates fabric of an earlier building, there
may be archaeological implications to such works
which would impact on the decision-making process.
Windows at attic level have been draught proofed. As
the upper level of the building is partially within the
roof space, the amount of insulation which can be
retrofitted may be limited owing to the construction
type of the roof and spatial considerations in the attic.
Under these circumstances a combined approach
needs to be taken with scope for lining the interior at
this level with insulation in tandem with filling the void
above the ceiling level with insulation where
accessible. This would provide the maximum
achievable levels of roof insulation. A range of
insulation materials could be considered for use in
such circumstances, with possibly more than one type
being required for different applications. The building’s
owners may have a preference for natural products
such as wool or hemp over synthetic products.
As with many historic buildings, the potential for
applying insulating materials to the interior face of the
walls is limited. The basement walls have been stripped
of their plaster, and a lime plaster finish could be
reinstated which would have a higher surface
temperature than the cold exposed stonework. Lime
plaster would also absorb and release moisture,
modifying humidity and adding considerably to the
sense of comfort within the room. Energy-saving works
which are carried out to the walls should also
concentrate on ensuring the walls are dry by
repointing them with lime mortar and re-plastering
with breathable lime plaster where necessary.
While some windows have window shutters, others do
not. In the case of the latter, consideration could be
given to providing new window linings with working
shutters. The shutters could be used at night time to
help retain heat gained in the building during the day.
Living over the shop
There may be some scope for inserting secondary
glazing panels inside the windows for the winter
months. These would be visually less obtrusive if a
relatively plain system (possibly in the form of two
sliding panels in a light aluminium frame) were
installed. This would allow ventilation as required, and
permit access for cleaning purposes.
Prior to draught proofing windows and doors, an
assessment of all means of ventilation of each room
should be completed to allow for proper consideration
and design for maintaining the minimum number of
air changes per hour in spaces that are heavily used.
Provision should be made to allow additional
ventilation to ensure that moisture and humidity levels
are controlled.
This building has historical importance which is an
over-riding consideration in the context of energy
savings. It would be best upgraded as follows:
> Through maintaining the building and ensuring
that the external walls are drier
Although this traditionally built building is not a
protected structure, it has been refurbished in
accordance with best conservation practice
> By improving roof insulation
> By fitting removable secondary glazing
> By reviewing electrical usage to provide light and
small power. Controls for lighting in this building
could be examined. Occupancy and daylight
detectors could easily be fitted
> Future development of the complex may provide
opportunities for more appropriate fitting of sustainable energy installations and for adding
extensions which, by their presence, could somewhat reduce the heating requirement of the
existing building. However, the restricted nature of
the site and the architectural significance of this
building would make the design of an appropriate
extension very difficult
This is a late-nineteenth century building, two-storeys
high over a basement with an inhabited dormer attic
storey, a first floor having tall windows and a ground
floor with a shopfront. It was originally built of brick
and stone, with a rendered finish to the rear façade. A
new return built in 2000 was constructed using a
proprietary metal system which has external
insulation as well as insulation between the metal
studs. The return extends over half of the original
north-facing rear wall. The building now comprises
two two-bedroom apartments with office use on the
ground and basement floors. The original windows are
single-glazed vertically sliding sashes.
At the time of its redevelopment in 2000, the
basement floors were replaced with a concrete slab
having an insulated screed containing a piped
underfloor heating system. Floors throughout the
remainder of the building consist of timber joists with
timber floorboards; new ceilings were added between
the shop floor and the apartments above, insulated
with mineral wool, primarily for fire separation
purposes, but which also has advantages in terms of
reducing noise transfer. The roof was re-slated and
provided with insulation to building regulation
requirements. At attic level, mineral wool insulation
was provided over the flat ceilings while insulation
board was provided to the coved areas. The original
walls of granite rubble and brick were left uninsulated.
The importance of this building arises from its
contribution to the character of the streetscape. The
building maintains its original appearance to the
street, except for the modern part of the shopfront.
The highly insulated extension on the north side was
constructed of steel studs with insulation between,
and with external insulation finished with a
proprietary render to the exterior. New windows are
timber framed with double-glazed units. The original
windows were repaired but not draught proofed. No
shutters were provided. An earlier aluminium
shopfront was removed and replaced with a new
timber-framed double-glazed shopfront.
Now approximately 130 years old, the refurbishment
works of 2000 should mean that this building will have
a further life of fifty to a hundred years before reslating is required. General maintenance works to
windows and cast-iron gutters will be required every
five years.
Appropriately designed and accurately detailed
shutters should be provided to all the original
windows which remain single-glazed.
There are individually controlled, gas-fired,
combination boilers to each apartment and the
ground floor offices. The common areas are unheated.
Having individual heaters for each tenant gives a high
degree of control over the use of energy and is an
efficient way of delivering heat to each tenant. The
building is part of a terrace which reduces the amount
of external wall and related heating load, while the
highly insulated new extension on the north side
reduces heat loss through the north wall by half by
‘internalising’ the older masonry wall over half its
A Georgian townhouse
The windows were provided with draught excluders
and the shutters were eased and adjusted to allow
them to be closed at night for security and insulation
purposes. After a short period of usage, some of the
draught excluders were removed to reinstate trickle
ventilation into the rooms to counteract the effects of
excessive heat given off by electrical office equipment.
All heating is by electrical heating. Consideration was
given during recent refurbishment to the installation
of a radiator-based system. However, the impact on
the historic fabric of the installation of the required
pipework would have been far greater than the
impact of wiring for storage heaters. Used judiciously,
storage heaters with convector fans can be cost
effective in traditional buildings, where they exploit
the greater thermal mass of such buildings. Individual
control on a floor-by-floor basis means that the rooms
are only heated as required. The stairhall is not heated.
A well-maintained Georgian house with its original
timber-framed sash windows
In common with most city-centre Georgian houses,
this building is now used as offices by a number of
different tenants. It is located in the middle of a
terrace, faces north, and comprises four storeys over
basement, with a typical floor plan having two rooms
per floor for the ground and first floor, the equivalent
rooms being subdivided to form four rooms on the
upper floors. The basement is used as a conference
room. A return structure is used as a residence. The
plan form of the building is compact, with a relatively
small amount of exposed external walling to the front
and rear.
Windows have been draught proofed and electrical
heaters upgraded to high-efficiency commercial
storage heaters, which fit under the windows,
replacing older storage heaters and inefficient plug-in
heaters. As the building is in commercial use, the
storage heaters are an effective way of heating the
spaces, providing heat efficiently during the day. The
shutters are all in working order and used at night
time to retain the heat which has built up during the
day. This building achieves comfort for a range of
different building users, who control heating levels in
each separate occupancy. The mid-terrace location
means that aggregate heat loss is relatively low.
Selective structural repairs were carried out to this
building, but apart from the conversion of the
basement to use as a lecture theatre, there has been
little alteration of this building. Much of the original
fabric has survived, the building having a resultant
high degree of architectural authenticity.
Now over 200 years old, this building is in good
condition and the recently completed structural repair
works will safeguard it for the foreseeable future. The
roof has not been re-slated in recent years and this
may need to be undertaken within the next 30 years.
General maintenance works to windows, cast-iron
gutters, and cast and wrought-iron railings will be
required every five years.
The existing insulation in the roof space is minimal
and should be upgraded where roof spaces or lofts are
accessible. Where ready access to loft spaces is not
possible, for example because of the lack of access
hatches, insulation provisions should be reviewed as
part of any future re-roofing works.
Places of worship
Caution should be exercised to ensure that any
electrical wiring in the roof space is in good condition
if it is to be enclosed by insulation. In some cases it
may be advisable to have wiring inspected by an
electrician on the Register of Electrical Contractors of
Ireland (RECI) before proceeding with installing
insulation. It is also very important to ensure that any
lights recessed into the ceiling have adequate
ventilation or fire-covers fitted before laying
Improvements to the heating system such as replacing
a boiler and installing better controls are good actions
to take. While it may seem extravagant, it is important
to seek to maintain the temperature of the church at a
reasonable level, probably over 12ºC, throughout the
week, so as to avoid condensation and damp-related
problems and to make it easier to achieve a
comfortable temperature during weekend services.
A nineteenth-century rural
A typical place of worship has decorative finishes both
internally and externally; rich with traditional materials
and details, they can be difficult to upgrade. In general,
the most appropriate energy-efficiency measures for
churches and cathedrals are the insulation of the roof
and the improvement of the mechanical and electrical
The upgrading of roof insulation is generally
straightforward where there is an attic in a building;
however, places of worship often have exposed
undersides to roofs, the upgrading of which requires
careful consideration. Where a place of worship has a
flat ceiling, it is generally possible to insulate above it.
Such insulation is inexpensive to install and has the
effect of moderating heat loss so that temperature
fluctuations between heating cycles are less extreme;
sudden changes in temperature can be damaging to
historic building fabric. Given that churches are often
only heated at weekends, it could be argued that there
is a long payback period on the investment in
insulation; this needs to be considered on a case-bycase basis. The episodic and variable way in which
such buildings are used also results in particular
requirements for its heating and lighting systems.
A nineteenth-century church with spire. The roof has
been re-slated and insulated and the walls re-pointed
This church dates from 1870 with various alterations
and additions having been made since. In plan, the
church comprises a three-bay nave with a tower and a
porch attached to the south west corner. A wide
chancel arch leads to the two-bay chancel while a
robing room adjoins the chancel on the south side.
The church has been well maintained over the years.
This church is usually used only twice a week for
services. During a recent programme of works to
improve the weathering of the building it was decided
also to undertake works to improve its energy
consumption and to increase the thermal comfort of
the building’s users.
The roof was re-slated with new Bangor Blue slate.
While re-slating the roof the opportunity was taken to
add a layer of insulation using a very thin layer of
reflective material between the slates and the ceiling
boards. This resulted in a slightly raised roof which was
accommodated with secret valleys at the barges and
raised gutters, supported by new stone insets. Walls
were repointed in a lime-based mortar to reduce
damp and internal lime plaster was repaired where
necessary. All lighting was replaced with low energy
metal halide lamps; with tungsten halogen lamps
confined to the sanctuary area to allow for
manipulation of the lighting levels.
A special detail was used to deal with the small
additional height that resulted from adding
insulation to the roof build-up; stone blocks were
added under the reinstated cast-iron gutter
Getting a gas supply to the site was not possible. The
oil-fired boiler was replaced with a more efficient one
and all pipework was replaced, lagged and fitted with
modern controls. New radiators were installed along
both walls of the nave at regular intervals to deliver
quick response heat to all areas in a short period of
time in accordance with the requirements of the users.
The result is a church which is draught-free with
controlled ventilation and an efficient, quick-response
heating system providing comfort levels when
While re-slating, the opportunity was taken to put the
original ceiling vents back into working order. The
vents are mechanically controlled to allow the users
to alter the amount of ventilation as required
An eighteenth-century
city church
This new extension to the rear of the church provides
necessary office accommodation and comprises two
storeys built on top of the ruins of the original vestry
The church following restoration
This church is intensively used both during the week
and at weekends. A programme of works was
undertaken a number of years ago to refurbish the
building for its current use. The building had suffered
from serious damp ingress over time and required
works to the roof, rainwater goods and stone façades.
As part of these building works, an extension was
added to the rear of the building and underfloor
heating was provided. Mineral wool insulation was
provided over the main ceiling. The existing singleglazed timber framed windows were repaired and
refurbished but not draught proofed.
As this building has long periods of continuous use at
a time, underfloor heating is an appropriate heating
system. The low-temperature heat stored in the floor
can help to combat ground damp in older buildings.
High spaces such as are found in big churches are
difficult to heat satisfactorily using radiators. By
heating the floor, heat is provided where it is required;
the convection of hot air is reduced, meaning that
overall heat losses are reduced. However, as many
places of worship have high quality flooring and, in
some cases, burials beneath the floor, the installation
of underfloor heating will often not be an option. The
lifting of a historic floor in a protected structure is of
course subject to planning permission. In this case, the
existing floor was timber with some tiling at the
perimeter but was in a dilapidated state and required
A timber glazed porch was provided inside the main
west door, primarily for draught-proofing purposes
but also to avoid having to re-hang the external
doors, which would otherwise be required to open
outwards for emergency egress
Historic buildings and the law
Under Part IV of the Planning and Development Act 2000, buildings which form
part of the architectural heritage can be protected either by being designated a
protected structure or by being located within an architectural conservation area.
Where a building is a protected structure (or has been proposed for protection) or
is located within an architectural conservation area, the usual exemptions from
requirements for planning permission do not apply. In the case of a protected
structure any works, whether internal or external, which would materially affect its
character, will require planning permission. Legal protection also extends to the
land and other structures associated with a protected structure such as outbuildings that are located within the curtilage of the main building. In an architectural
conservation area, any works to the exterior of a building which would affect the
character of the area also require planning permission. Owners and occupiers of
protected structures have a responsibility to maintain their buildings and not to
damage them or allow them to fall into decay through neglect.
A notice was sent to every owner and occupier of a protected structure when the
building first became protected. If you are not sure of the status of your building,
check the Record of Protected Structures in the Development Plan for the area. If
your building is a protected structure, or if it is located in an architectural conservation area, your planning authority will be able to tell you what this means for
your particular property.
As an owner or occupier of a protected structure, you are entitled to ask the planning authority to issue a declaration which will guide you in identifying works
that would, or would not, require planning permission. Works to upgrade the
energy efficiency of a protected structure, if carried out in line with good conservation practice and the guidance contained within this booklet, will generally not
require planning permission if they do not materially affect the character of the
building. However, some types of work may require planning permission. If you
are in any doubt about particular proposed works, you should contact the architectural conservation officer in your local authority for advice.
For general advice on planning issues relating to architectural heritage, a publication entitled Architectural Heritage Protection Guidelines for Planning Authorities
(2004) published by the Department of the Environment, Heritage and Local
Government is available from the Government Publications Sales Office or can be
downloaded from
Generally, an existing building is required to comply with the Building Regulations
when it undergoes a material alteration or change of use. Technical Guidance
Document (TGD) L is published by the Department of the Environment Heritage
and Local Government to provide guidance on meeting the requirements for Part
L: Conservation of Fuel and Energy of the Building Regulations. The guidance is published in two parts, one for the Conservation of Fuel and Energy - Dwellings and a
second for the Conservation of Fuel and Energy - Buildings other than Dwellings.
These documents set out a number of minimum standards for heat loss, thermal
bridging, air infiltration and the efficiency of heating and cooling plant.
An existing building which is a protected structure or a proposed protected
structure is exempt from the requirements of Part L (Conservation of Fuel and
Energy) of the Building Regulations when it is subject to material alteration or a
change of use. Buildings protected under the National Monuments Acts, such as
recorded monuments, are generally exempt from the requirements of the
Building Regulations. A number of categories of buildings are exempt from the
requirements of the European Communities (Energy Performance of Buildings)
Regulations 2006 which require a Building Energy Rating (BER) to be undertaken
for an existing building when let or sold. These categories include buildings protected under the National Monuments Acts, buildings that are protected
structures and proposed protected structures under the Planning and
Development Acts and buildings used as places of worship or for the religious
activities of any religion.
Any works that would affect the character of the building or have a material or
visual impact should be carefully considered. In specific cases, relaxation of
requirements may be acceptable to the local building control authority, if it can
be shown to be necessary in order to preserve the architectural integrity of the
particular building.
The Building Control Acts and associated Regulations apply minimum standards
to the design and construction of extensions, alterations and change of use of
existing buildings; responsibility for complying with the Building Regulations
rests primarily with the owners, designers and builders of the buildings or works.
The current Building Regulations and Technical Guidance Documents can be
found at
Useful contacts
The architectural conservation officer in the local authority should be the first person to contact with queries
regarding a historic building. Other useful contacts include:
Architectural Heritage Advisory Unit,
Department of the Environment, Heritage and Local Government,
Custom House, Dublin 1
Telephone: 01 888 2000
Construction Industry Federation, Register of Heritage Contractors, Construction House, Canal Road, Dublin 6
Telephone: (01) 406 6000
Engineers Ireland, 22 Clyde Road, Ballsbridge, Dublin 4
Telephone: 01 665 1300
Heritage Council, Áras na hOidhreachta, Church Lane, Kilkenny, Co. Kilkenny
Telephone: (056) 777 0777
Irish Architectural Archive, 45 Merrion Square, Dublin 2
Telephone: (01) 663 3040
Irish Georgian Society, 74 Merrion Square, Dublin 2
Telephone: (01) 676 7053
Royal Institute of the Architects of Ireland, 8 Merrion Square, Dublin 2
Telephone: (01) 676 1703
The Society of Chartered Surveyors, 5 Wilton Place, Dublin 2
Telephone: (01) 676 5500
Sustainable Energy Authority of Ireland, Wilton Park House, Wilton Place, Dublin 2
Telephone: (01) 808 2100
Further reading
Baker, Paul. In Situ U-Value Measurements in Traditional Buildings – preliminary results. Edinburgh: Historic
Scotland. (2008)
Baker, Paul. Thermal Performance of Traditional Windows. Edinburgh: Historic Scotland (2008)
BRECSU. Post-Construction Testing – a professional’s guide to testing housing for energy efficiency. General
Information Report 64. London: HMSO (2000)
Carrig Conservation et al. Built to Last: the sustainable reuse of buildings. Dublin: Dublin City Council (2004)
Changeworks. Renewable Heritage - a guide to microgeneration in traditional and historic homes. Edinburgh:
Changeworks (2009) downloadable from
Changeworks. Energy Heritage - a guide to improving energy efficiency in traditional and historic homes.
Edinburgh: Changeworks (2008) downloadable from
Cook, Martin Godfrey. Energy Efficiency in Old Houses. Wiltshire: Crowood Press (2009)
Department of the Environment, Heritage and Local Government. Architectural Heritage Protection-Guidelines
for Planning Authorities. Dublin: The Stationery Office (2004)
Department of the Environment, Heritage and Local Government. Technical Guidance Document L
Conservation of Fuel and Energy - Dwellings. Dublin: The Stationery Office (2008)
Department of the Environment, Heritage and Local Government. Technical Guidance Document L
Conservation of Fuel and Energy - Buildings other than Dwellings. Dublin: The Stationery Office (2008)
Energy Savings Trust. Energy Efficient Historic Homes - Case Studies. London: Energy Savings Trust (2005)
English Heritage. Energy Conservation in Traditional Buildings. London: English Heritage (2008)
European Union. Directive on the Energy Performance of Buildings. (2002, recast 2010)
Historic Scotland. Conversion of Traditional Buildings - Guide for Practitioners. Edinburgh: Historic Scotland
National Standards Authority of Ireland. The Installation of Solar Heating Systems. Publication forthcoming
O’Cofaigh, E, Olley, J A and Lewis, J O. The Climatic Dwelling: an introduction to climate-responsive residential
architecture. London: Earthscan Publications Ltd (1996)
Office of Public Works et al. Green Design: sustainable building for Ireland. Dublin: The Stationery Office (1996)
Sustainable Energy Ireland. Energy in the Residential Sector. Dublin (2008)
Wood, Chris, Bordass, Bill and Baker, Paul. Research into the Thermal Performance of Traditional Windows:
Timber Sash Windows. London: English Heritage (2009)
Biodegradable fraction of products, waste and
residues from agriculture (including vegetal and
animal substances), forestry and related industries, as
well as biodegradable fraction of industrial and
municipal waste, used as a fuel or energy source
Energy from renewable non-fossil energy sources, for
example solar energy (thermal and photovoltaic),
wind, hydropower, biomass, geothermal, wave, tidal,
landfill gas, sewage treatment plant gas and biogases
A type of masonry construction comprising two leaves
of masonry separated by a gap, or cavity, to prevent
moisture from the outside transferring to the inside
The replacement of mortar in the face joints of
brickwork or stonework following either the erosion of
the original mortar or its removal through raking out
An impervious layer built into a wall to prevent
moisture penetrating the building
The heat absorbed by a building arising from its
exposure to sunshine
This occurs when a portion of the construction of a
building is colder than the surrounding construction,
leading to condensation and possible mould formation
on the cold surface. Also known as ‘cold bridging’
Energy supplied to a building and its systems to satisfy
the relevant energy uses, for example space heating,
water heating, cooling, ventilation or lighting.
Delivered energy does not include renewable energy
produced on site
The ability of a building to absorb and store heat
The energy used in the manufacture, processing and
transport of a material
Technologies that produce heat and electricity at a
small scale including solar panels, photovoltaic panels,
domestic wind turbines, heat pumps and the like
The application of lime mortar to the underside of roof
slates or tiles
A type of photography that uses infra-red sensitive
cameras to produce images which map the amount of
heat emitted by an object
Unplasticised Polyvinyl Chloride is a type of plastic
vinyl used for making window frames, doors, rainwater
pipes and some types of roof coverings
Arrays of solar cells containing a semi-conducting
material that converts solar radiation into electricity
A measure of the rate of heat transfer through a
material expressed in W/m²K: the faster the rate, the
higher the U-value, therefore better insulators have a
lower U-value
A material such as ash, sand or shells laid between
floor joists or packed within partition walls to provide
sound insulation
A mixture of a binder (such as lime or cement), an
aggregate and water to form a coarse plaster which is
applied to the external surfaces of walls
The total cost of constructing and using a building
over its life. The whole-life cost of a building includes
the initial capital cost of building it (and all ancillary
design and other costs) and the cost of operating and
maintaining it over the period of its useful life
The Advice Series is a series of illustrated booklets published by the
Architectural Heritage Advisory Unit of the Department of the
Environment, Heritage and Local Government. The booklets are
designed to guide those responsible for historic buildings on how
best to repair and maintain their properties.
advice series
advice series
advice series
advice series
advice series
advice series
Understanding how a traditionally built building works and how
to maximise the levels of comfort for its occupants
Choosing the most effective and cost-effective options for
improving energy efficiency
Keeping a historic building in good health
© Government of Ireland 2010
Price a10
Traditionally b uilt buildings pe rform differently fr om modern
construction in the w ay they de al with da mp and atmo spheric
moistu re, and misguided wo rks ai med at improvin g their thermal
efficie ncy can have da maging consequen ces. This guide will help
you to m ake the rig ht decisions on how to increase the comfort and
reduce the energy u se of your histo ric buildin g by giving advice on:
Avoiding damage to the building by inappropriate works
advice series
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